Late to the party as usual, and I've probably missed this boat, but as I was contacted by Embala to take a look at this thread (what a fascinating topic! :D), I'm tossing in my rambling two cents in.
I also recall Cutter thinking on how Winnowill's name carries no inherent meaning, reflecting that its as empty as the wind howling through the barren branches of a winter-gripped forest.
As someone else pointed out, this may mean that her name has no meaning to a Wolfrider, which is a tribe with its own history and customs, rather removed from the High Ones. I don't think, necessarily, that its a case of High Elfin vs Low Elfin, but rather the idea that 'Winnowill' is a word that embodies an ancient concept that the High Ones had that their descendants don't. Thus the word has fallen out of use, out of memory.
What might this word mean? The very word 'Winnowill' makes me think of 'winnow will', as in the breaking down of another's will. This is essentially what she's done throughout the whole series, but I doubt her parents knew that.
In my little headcanon, Haken was Winnowill's father. He wasn't a peaceful, 'let's live in harmony with humans' kind of guy. He hated everything about Abode, but the humans most of all. I think he gave his daughter a name that embodied his hopes for her; Haken likely knew he would die before eradicating all of his enemies, and he'd want to pass on that legacy. He would want his child to destroy those who had harmed their people, breaking them through her power, subjugating them all. Winnowill, in my brain, means something like 'one who conquers', or describes one who might utterly dominate.
The Wolfriders don't really have a concept of conquest; that's a human idea.
That's just my idea; feel free to disregard! XD