It is popular among Messianic Jews to follow Evangelicals in revealing Pagan origins of Christian feasts. Messianic Jews of Evangelical orientation usually support these old discoveries with own Jewish witness: there had been nothing heard about any celebrations of Sunday in the Hebrew Bible, nothing has been attested in the apostolic times either. Therefore a celebration of Easter Sunday cannot be Jewish in turn. 
Of course, nothing is said in TaNaKH about the Resurrection of Messiah Y-shua. Every traditional (Halachian) Jew can affirm this fact. Now one goes further coming to the Trinity and finally comes to Talmud. A lot of divine triads (not Trinities!) are known in old pagan religions, starting from Ancient Egypt (to analyse their pantheistic origin as Emanation of the Primeval Sourse of the Universe, – cf. Kabbalah by the way, – clearly surpasses abilities of the “discoverers”). After such reasonings one should close Messianic Judaism for ever as a mistake. Then those Messianic Jews who still want to preserve their faith in Gospel, should convert into any Evangelical sect (especially where Charismatic Glossalalia are most loved today – nothing to do with Jewish tradition!), or to join those Halachian Jews who are tolerant to that “unhappy Y-shua ben Yoseph”, who “was a good lad but a loser, unfortunatley: almost-a-prophet, nothing more!”
As for Trinity, this is not a subject of a discussion now being a unique theological concept which can be neither negated, nor proved as belonging to the field of the apophatic theology with some hints given by G-d Himself on His nature – cf. Three-One in Gen 18, or such Jewish concepts as Metatron and Logos-Memrah, as well as the interchange of the field and the electron in physics, intuiting here a likeness to co-existence of OnlyOne-Three-TheInfinity of Separate (not any “Modes” of One!) Person/Persons of Eyn-Sof at once. All this CANNOT be a part of any dogmic “scientific research”, of course.
However our subject now is much more simple concerning usual human foolishness only. Most popular foolishness states the bad Constantin having shifted Saturday to Sunday. It is a foolishness to such a degree, that is not worthy to discuss here at all. However every “shocking” fool does not omit a possibility to “show” that Sunday means the day of Sun! No matter that the Greeks celebrate the Day of Lord (Kyriakē), as well as Armenians or Georgians, whose “Sunday” is correctly the FIRST day of the week (as in Hebrew), not the seventh day (the latter named with Hebrew Sabbath accordingly) as in the West.
However it  is not any foolishness to say that there is no traces of celebrating on Sunday in times of pupils of Messiah Y-shua: it is a mistake. 
Acts show that the pupils gathered on Sabbaths, Paul never travelled on this day. The sanctity of the Sabbathian rest is clearly confirmed by Messiah Y-shua in Matthew 24:19 (removed from Mark 13:18 by some Anti-Semitic Greek scribe on the break of the 1st / 2nd c. with all probability). Every Jew knows that the Sabbath ends with Havdalah. The earliest Christian liturgy clearly reflecting the Sabbathian wine-bread ceremony via the Last Supper, it is clear that this was practice of the first apostles themselves, but their Havdalah was therefore a greeting of the Resurrected Messiah Y-shua, or celebrating the First Day of the week (so-called “Sunday”) consequently. No doubt, breaking of bread took place after the sunset as a part of Hafdalah. Thus they broke bread already on the first day of the week: analyse the story of Eutychus in Acts 20:7–11, especially 20:11 if only you still possess a sane brain, of course:
Having reanimated Eutychus, Paul came back upstairs again to break bread – when? was it on Monday? – They lingered on “till midnight” (20:7), however a next day begins after the sunset, not after midnight as today among non-Jews. Was it that they missed the whole “Sunday” (the day of Resurrection) in speaking and understood this in a hurry when it was too late to break bread after Monday had come? Or they simply kept the Sabbath rest till coming evening and got together before the sunset in order to break bread after it on the first day of the week, i.e. on Sunday, the Day of Resurrection? Who breaks bread 24 hours long! 
Thus breaking the bread, or Eucharist, is namely celebration of “Sunday”, when Sabbath is a Day of resting, dedicated to G-d, which was never “shifted” to Sunday by nobody till post-hoc Roman catholic explanations. However it was a local council of 37 bishops Anti-Semites in Laidicea who tackled annulling the whole “Jewish Decalogue” at all (a phrase “if you CAN”). 
The best evidence of continuity of this apostolic practice is found in section 14-1 of the earliest known Christian Catechism named Didache (break of the 1st / 2nd c.):  On each Lord's day having gathered yourselves together, break bread, and give thanksgiving.
This is why Constantin, wishing to favour Christians, made officials and soldiers free from duties “on Sun's day” in order they could participate in the Eucharist. No word is about „Saturday“ because since Roman-Jewish wars gentile Christians used a possibility to gather on Sundays for the Eucharist in order not to be associated with the rebels Jews. Thus Roman (and Alexandrine) Christianity was Sunday-oriented from the very beginning, trying to find peace with Roman authorities at the expense of the Jews, “enemies of the Empire”. Constantin having legalized Christianity, all these loyal Roman citizens became finally patriotic and Anti-Semitic consequently. No “Roman-Catholic Church” existed there yet, but when having formed itself later, it only inherited the Roman imperialism for all further times.
Here one sees an answer, for what crime the Jewish nation was punished with “supersession” of their chosenship with that of the Gentiles:  G-d they ostensibly murdered was the Roman Empire! One also sees how Anti-Semitism spread further through the mediation of Martin Luther up to Auschwitz. Speculations with religion are known means to justify own imperialism (cf. e.g. situation in Baltic where “explanations” arose, beginning from Orthodox Church leaders and finishing with modern Dugin's doctrine, that the Great Duchy of Lithuania had been Russian from the very beginning).
One also sees here a reason of the decay of today Gentile Christianity: it started with erasure of the Lord's words in the Gospel (Mk 13:18) even at the boundary of the 2nd c., thus becoming subject to eternal words of Unchangeable G-d in Gen 13:2.
Messiah Y-shua resurrected on the First Day of the week thus fulfilling the sense of the Sabbath in the eschatological Eighth Day of (Re)Creation of the world, a kind of independent Catholic and Talmudic idea by the way, cf. also Hebr 3:17 – 4:11.

Turning back to human foolishness, let us examine how ostensible Pagan origin of Easter is being usually portrayed. Similarly as in the case of Sunday, all “shocking inventions” are made in frames of English and Germanic world, fully forgetting that no such term has ever existed in Christian Orient. With only clicking “Easter Eastre” one finds tons of dilettante publications on web retelling one from another the same idea that Easter comes back to Old Germanic Goddess Eostre (persons ignorant in lingustics, immediately add “similarly sounding” Ishtar (Astartha) as an ostensible cognate of the same name...: what a horror that Catholics worship Astharta instead of “Jesus”!)
It should be made clear that the invention of this Goddess belongs to a short inventive note about Old Pagan Deity of spring months Eostre by “Venerable Beda” (ca. 673–735), author of the “Church history of the English nation”. This idea was used by Jacob Grimm in his “German Mythology” during the burst of the German nationalism with its especial interest in “gloriuos pagan past” (what was a typical result of emancipating of peasantry in the West for the sake of progress of agrarian production at the expense of partition of big manors and abolishing feudal manorial rights, by the way). Jacob Grimm uncritically “restored” such a Germanic deity of spring, Ostara, equalling her to Latin Aurora on the German linguistic grounds (cf. a cognate Lith. Aušra / Aušrinė). Therefore Grimm's “evidence” got even into serious scholarly literature. A classical Etymological Dictionary of the German language should be cited here for a modern most authoritative scholarly explanation:

Ostern Pl. mhd. ōsteren, ahd. ōstarun, ags. ēastron, engl. Easter. In einem nd. Gebiet (Frings, Idg. Forsch. 45, 267 ff., K. Bischoff, Zs. f. Mundartig. 21, 28), gilt Pāsche(n) in einer Randzone an der nl. Grenze. Entspr. nl. pasen, asächs. afries. pāscha, anord. pāskar, got. paska, wie frz. pâque aus kirchenlat. pāsca, das Hebr. Ursprungs ist. Ostern wird zu aind. usrā ‘Morgenröte’ gestellt. Man meinte Aorōra sei den Germanen wenigstens teilweise aus der Tageslichgöttin zur Lichtgöttin des Frühlings geworden. Ihr westsächs. Name *Eastre sei durch Eostre bei Beda († 735) gesichert. Aber eine solche germanische Göttin ist nicht erwiesen, und die Bedeutung ‘Frühling’ gibt es in keiner idg. Sprache. Ostern ist gallo-fränk. Prägung zu *austrō ‘Morgenrot’ (s. Osten) nach lt. albae (paschales), alba ’Morgenrot’, von da aus ags. frühahd. Auferstehungsliturgie am Morgen. J. Knobloch, in: Die Sprache 1959, 27. Wortatlas XVI.

Ostern [‘Easter’] pl. MHG ōsteren, OHG ōstarun, AGS ēastron, ENG Easter.  In a North-German zone bordering Netherlands (Frings, Idg. Forsch. 45, 267 ff., K. Bischoff, Zs. f. Mundartig. 21, 28), Pāsche(n) is in use. Corresp.: Netherland. pasen, AGS OFries. pāscha, ONord. pāskar, Goth. paska, as well as Fr. pâque come from Church-Lat. pāsca of the Hebrew origin. Ostern corresponds to Skr. usrā ‘Morgenröte’. One thought that among German tribes Aorōra should have at least partly been transormed from the Goddess of Light into a Goddess of Spring.  Her WSachs. name *Eastre seemed to have been grounded by Beda († 735) with his Eostre. However an existence of such Germanic Goddess has not been proven. Even more: no word of this root has a meaning ‘spring’ in any I.-E. language! Ostern is a Gallic-Frank coining of *austrō ‘morning twilight’ (s. Osten) for Latin albae (paschales), alba ‘morning twilight’ giving an AGS early OHG name to a Resurrection Mass in the morning. J. Knobloch, in: Die Sprache 1959, 27. Wortatlas XVI.

Fr. Kluge, Etymologisches Wörterbuch der deutschen Sprache. Walter de Gruyter, Berlin - New York 1975, p. 526.

Sapienti sat!  There is no hope to persuade maniac fools, some of whom will further ‘prove’ their beloved pagan goddesses and blame Christus–Krishna, the others blaming bad Catholics who worship these goddesses together with Santa Claus, who is Satan Claus. The tragedy is when Messianic Jews repeat all these foolish things showing themselves being simply evangelicals who play Jews.

This publication is a negation of a pagan origin  of traditional Christian feasts, not any attempt to negate pagan folklore elements in them.