Again, I’m not a historian but there’s some evidence to the contrary. The TL;DR is that Easter is a Christian holiday but secular traditions became associated with it centuries later:
"The earliest certain attestation of the Easter bunny dates to 1682, in a pamphlet titled Satyrae medicae continuatio XVIII disputatione ordinaria disquirens de ovis paschalibus (‘continuation of a medical satire no. 18, enquiring in a serial disputation on the subject of Easter eggs’) by G. Franck von Franckenau, published in Heidelberg,…:
In Germania Superiore, Palatinatu nostrate, Alsatia et vicinis locis, ut et in Westphalia vocantur haec ova di Hasen-Eier a fabula, qua simplicioribus et infantibus imponunt Leporem (der Oster-Hase) eiusmodi ova excludere, et in hortis in gramine, fruticetis et c. abscondere ut studiosius a pueris investigentur, cum risu et iucunditate seniorum. Et revera saepe leporum, h. e. Imprudentium nomine possunt venire, qui eiusmodi ovis exposititiis non solummodo iocos quaerunt: Siquidem saepe cum illis ovis pueri valetudinis suae magnam inveniunt iacturam; quando dein, semoto arbitro, ista iusto avidius per ingluviem ingurgitant, sine sale, butiro, aut alio condimento; …
In Upper Germany, (my) native Palatinate, Alsatia, and neighbouring regions, as also in Westphalia, these eggs are called ‘the Rabbit Eggs’, because they have a custom for simple people and children that a Rabbit – ‘the Easter Rabbit’ – hides the eggs in such a manner, and conceals them in gardens in the grass, fruit trees and so on, for them to be hunted out very carefully by children, to the laughter and amusement of their elders. And in fact people can sometimes come by the name of ‘rabbits’, that is, fools, if they search when eggs are hidden in this way not just as a joke. In fact children often do serious damage to their health with these eggs, if their guardian is absent, if they devour them too greedily out of gluttony, without salt or butter or other condiment …
(The pamphlet goes on about the eggs, but doesn’t mention the rabbit again.)
There are claims floating around that there’s an earlier reference to the Bunny dating to 1572. As pointed out to me earlier this year (offsite) by someone going under the name of ‘Marvin’, this is a misattribution derived from a 1933 article –
Vielleicht spielt auch schon Fischart in ‘Aller Praktik Grossmutter’ (1572) auf den Osterhasen an, wenn er sagt: ‘Sorg nicht, dass dir der Haas vom Spiess entlauf: Haben wir nicht die Eier, so braten wir das Nest’.
Perhaps Fischart also already played on the Easter Rabbit in ‘All Grandma’s customs’ (1572) where he says: ‘Don’t worry if the Rabbit escapes from the spit: if we don’t have the eggs, we’ll cook the nest’.
However, the 1572 source doesn’t contain this line: it actually comes from Sander’s Gargantua und Pantagruel vol. 3, page 420, published in 1787. How the 1933 article came to misattribute the line is beyond my knowledge.
Anyway, that means the line is nearly a century later than the actual earliest attestation. Franck von Franckenau, in 1682, remains the earliest source for the Easter Bunny.
There is incidentally no evidence for any link between rabbits and the pre-Christian English goddess Eostre, attested by Bede in the early 700s. I once thought this link was suggested by Jacob Grimm in his Deutsche Mythologie (1835), albeit purely as a speculation, but now that I look at Grimm again I don’t find any such suggestion there. I’m not certain what the origin of that supposed link is.
There are various reports of alternative Easter critters in Germany up to the early 20th century (and potentially later), such as the Easter Fox and a Franconian Easter Stork. To the extent that they are legitimate, they would tend to indicate that the Easter Bunny originates in a German Easter Critter of indeterminate species, but I don’t have anywhere to point for good documentation for them: I can vouch for Franck von Franckenau’s Oster-Hase, I can’t vouch for the other critters."
If this is true, then the order goes Easter --> secular/Germanic traditions rather than traditions --> Easter. But this is not my area of expertise and I am open to evidence that the r/AskHistorians person quoted above is wrong.
I am genuinely curious so I read the article and looked into its primary sources. The scientific citations actually contradict the premise of the article.
They begin by noting the earliest written connection that we have of the Easter bunny and hiding eggs:
The historians I cited earlier said as much. Then the smithsonianmag article notes a scholarly hypothesis from the novelist/linguist/mythologist Jacob Grimm:
The connection between the goddess and the Easter hare was speculated by brother Grimm in the 19th century and has no ancient basis. Bede never links Eostre to hares, rabbits, or any fertility symbols. See Lauritsen et al, which smithsonainmag.org cite as support of “pagan roots”, explicitly noting the lack of evidence:
The suggestion throughout Lauristen et al is that the name Eostre, the name of the month, was pre-Christian. Similar to how “Thursday” comes from “Thor’s Day” (but that doesn’t mean we worship the Norse god Thor). But there is no evidence, as far as I can tell, that a pre‑Christian festival celebrating Eostre coincided with the Christian feast of the Resurrection or involved any of the animals now associated with Easter. The claim that early Christians reappropriated pagan traditions appears unsubstantiated.