Note: for some reason a first draft of this post published instead of the edited version. That’s now fixed.

From: Andrea
Having visited Whitby some years ago, I found Hild especially intriguing. I’m writing to suggest that someone might like to add a reference to it at the Wikipedia article about freemartins (your book was the first time I’d ever heard of them.
There already is a Wikipedia article on freemartins. But, yes, it would be fab if someone added Hild to the list of fictional uses. Actually, it would be lovely if people would fix/add to my Wikipedia entry and/or create something for Hild. I can’t do it myself, for obvious reasons: it would be against Wikipedia’s rules; it would feel hinky (and most definitely un-English); and, well, I’m lazy I have Hild II to write. But if anyone out there wants to give it a go, I’d be more than happy to offer assistance.

Freemartins have been around longer than recorded history. But where does the word come from? Most people divide it into two parts, with martin being the easiest to deal with. The OED offers “Of unknown origin: cf Ir., Gael, mart, heifer.” On further investigation (that is, a quick cruise through the first two pages of search results) mart is Middle English for cow or ox fattened for market. 
That might be from the French which is from the Latin (which might, depending on how you trace it, originate with the Etruscan *merk—). Mart is also a term that was apparently used relatively recently in Scotland—from the Gaelic, which of course originates with Old Irish. Both, naturally, begin with Indo European… 

Free is even trickier. a bit trickier though, again, you could link it to Old Irish fiadh, which means (roughly) wild. But why “wild”? We’re really reaching…

In the end, I don’t think there’s any way to tell. But the only way to know for sure is to delve deep, and to consult experts. (And see above, for why I’m not likely to bother just now.) So let’s just say people in Hild’s era may or may not have used the word, but freemartins have been around since the domestication of cattle. (And sheep, goats—yep, they have them too.)

And, hey, it makes a great metaphor.