I've blogged extensively about Eostre in the past and don't intend to repeat any of that here. The short version: there is only one reference to her anywhere, in Bede; he gives absolutely no information about her except for her name; and everything else that people claim about her, such as having a sacred hare companion, is wholly unsupported by evidence.
This is not even a controversial stance. On the contrary, it is exactly what the Oxford Dictionary of English Folklore states: 'Nowadays, many writers claim that hares were sacred to the Anglo-Saxon goddess Eostre, but there is no shred of evidence for this; Bede, the only writer to mention Eostre, does not link her with any animal.'
The interesting question now, to me, is when this spurious association between Eostre and hares arose. It's not in Bede, as we've already established. It's not in Grimm. (EDIT: WRONG, SEE FURTHER EDIT NOTE BELOW.) Adolf Holtzmann, writing in 1874 in German Mythology, states "The Easter Hare is unintelligible to me, but probably the hare was the sacred animal of Ostara." This is the earliest example of this association I can find, and it is still speculative at this point.
K. A. Oberle, in the catchily titled Überreste germanischen Heidentums im Christentum, oder die Wochentage, Monate und christlichen Feste etymologisch, mythologisch, symbolisch und historisch erklärt (1883), writes "Wahrscheinlich ist der Hase das heilige Tier der Ostara gewesen" (Probably the hare was the sacred animal of Ostara), echoing Holtzmann.
However, it's worth noting that in 1892, Charles J Billson writing in the the British journal Folk-Lore states flatly that "Oberle also concludes that the hare which lay the particoloured Easter eggs was sacred to the same goddess," ignoring the 'probably' that both Holtzmann and Oberle included.
We find another speculative association in Charles Isaac Elton's Origins of English History (1890), in which it is suggested that certain Easter customs "were probably connected with the worship of the Anglian goddess Eostre", the customs in question being those in which "the profits of the land called Harecrop Leys were applied to providing a meal which was thrown on the ground at the 'Hare-pie Bank".
Elton's speculation is still a far cry from the modern assertion that Eostre's sacred beast was the hare, so who first made that assertion? John Lanyard's Lady of the Hare (1944) refers back to Billson, but writes as if the question were more or less settled, rather than being a matter of speculation: 'Since the Saxon Easter Goddess does seem to have been connected with the hare, and the hare so widely symbolizes 'dawn', and as dawn comes from the east, and Easter is the festival of the Resurrection symbolizing the birth of new life, it had occurred to me to wonder whether the actual word "Easter" might have a very simple explanation indeed - so simple that philologists and churchmen alike had missed it - namely that it was cognate to the word "east" as symbolizing the dawn from which new light came.'
By 1976, we have Christina Hole writing in Easter and its Customs: 'The hare was the sacred beast of Eastre (or Eostre) a Saxon goddess of Spring and of the dawn.' Any suggestion that this is a speculative association is entirely extinct. Somehow, along the way, supposition has become unexamined fact. I am not aware of any source between John Lanyard and Christina Hole who makes this outright statement, and would welcome any breadcrumbs from readers of this blog who know of one.
So, in summary, here is a very tentative timeline of Eostre's Bunny:
725 CE: Bede mentions Eostre. He does not associate her with hares.
1835 CE: Grim, in Deustche Mythologie, postulates Ostara; he does not associate Eostre with hares. (WRONG - SEE EDIT)
1874 CE: Adolf Holtzmann states 'probably the hare was the sacred animal of Ostara'.
1883 CE: K.A. Oberle also states 'probably the hare was the sacred animal of Ostara'.
1890 CE: Charles Isaac Elton states that Easter customs at 'Hare-pie Bank' at 'Harecrop Leys' 'were probably connected with the worship of the Anglian goddess Eostre'
1892 CE: Charles J Billson refers to Oberle's association of the hare with Ostara as a conclusion, rather than as a speculation
1944 CE: John Lanyard states that 'the Saxon Easter Goddess does seem to have been connected with the hare'.
1976 CE: Christina Hole states that 'The hare was the sacred beast of Eastre (or Eostre) a Saxon goddess of Spring and of the dawn.'
Please bear in mind that no new evidence arose during this time to change the speculative association into a definite one. The shift from 'probably the hare was the sacred animal of Ostara' to 'the hare was the sacred beast of Eastre' wasn't based on any archaeological discoveries, collected oral traditions or unearthed documents. It appears to have been based completely upon authors borrowing from other authors, and in so doing, shifting the goalposts of certainty until one person's speculation had become another's unchallenged fact.
Afterword: it's an interesting time in Eostre studies, folks. As you'll know, I have never been inclined to dismiss Eostre herself out of hand, though I am happy to take the axe to the massive amount of unsupported codswallop that is circulated concerning her, such as the bunny story. As far as Eostre herself goes, if she's good enough for Professor Hutton, she's good enough for me. She may have been a real figure of worship, she may not. The jury's still out on that one.
And now Doctor Philip A. Shaw of the University of Leicester has added something entirely new (to me) to the ongoing debate, namely linking Romano-Germanic votive inscriptions to the 'matron Austriahenea' to Eostre. I am therefore going to pick up a copy of his work 'Eostre, Hreda and the Cult of Matrons' just as soon as the next pay cheque arrives. Though one does have to facepalm at the sole comment on Amazon: 'It is not surprising that there is little "hard evidence" considering that there was literally a war waged over hundreds of years to stamp out "the old religion."' I imagine Dr Shaw would probably have a few words to say on that, too.
EDIT: This is fascinating stuff. According to Swain Wodening's review of the book, Dr. Shaw believes that Eostre really existed but that she and Hretha were entirely local to Kent! So, the selfsame academic who offers up new evidence for Eostre's existence also limits her to a very small part of south-eastern England. Not a pan-Germanic Goddess at all, then; and in affirming an entirely local Kentish Eostre, Dr. Shaw is effectively demolishing the hypothetical Germanic 'Ostara' proposed by Grimm. Indeed, he suggests that 'the German month names Ostermonat and Redmanot were carried to Germany and France by Anglo-Saxon missionaries, and uses this to back his claim that they were local goddesses'! So, the stance is that Christian Anglo-Saxons took those month names over, and (presumably) there is no connection at all to any cognate pagan goddesses in those regions. Well, that certainly jives with Charlemagne renaming the month of April to the old High German Ostarmanot; he would hardly have done so if there were lingering pagan associations.
IMPORTANT EDIT: I done screwed up, folks. Bound to happen one of these days. Holzmann's Deustche Mythologie was simply a reissue of Grimm. So it *was* Grimm who made the initial association between Ostara and hares. I'm going to leave the original with this correction in place rather than edit it out, because I'd rather not pretend to be infallible.
Next Easter Rant: the Pagan Sausage Machine Fallacy