Bigfoots or Bigfeet?

I was reading a book called Bigfoot vs. Chupacabra in which this issue was raised. I suspect it derives from Tolkien, per the Proudfoots vs. Proudfeet dispute.

• What is the proper plural of the colloquial American term for Sasquatch?

The book also touches on Yeti, which seems to be both singular and plural, although "Yetis" is proposed as a correct, if less graceful, alternative. I mention it because there may be a plural usage for Bigfoot: "Stay away from the crick--there's a herd of Bigfoot down there eatin' blueberry bagels."

As I am regularly accused of assaulting the English language, I though I'd bring it to the experts.

This question on "mouses vs. mice" provides some very good insight, but I'm also interested in these specific terms, and the idea of the plural use of the singular form, thus Yeti/Yeti/Yetis. (In other words, it also relates to deer and deer (singular and plural, respectively.)

Solution 1:

There isn't really any way to define a "proper" plural for a colloquial term for a mythical creature.

English plural formation, although mostly regular, permits an indefinite amount of irregularity for any particular word. Consider the case of people, which is, at least from an etymological standpoint, a suppletive plural form of person that is not related at all (from a synchronic standpoint, I suppose the initial "p" that these words have in common could be considered a shared element, although it's not clear what type of element it would be).

From what I understand, a hypothesis has been proposed that plurals or other inflected forms have to be formed regularly if they are compounds and the last element is not the semantic head, but there isn't clear evidence that this hypothesis is true and there are a fair amount of counterexamples. To me, it seems more like an argument based on the logic of how it seems pluralization should work than an actual established fact about how pluralization does work. See the following Language Log posts by Mark Liberman:

• Systematic Irregularization
• Flew v. Flied

In a whimsical context, someone might even use an "improper" form deliberately: does that mean it should be considered "proper" in a way after all? It just seems like a matter of opinion to me. (E.g. consider the relatively common fanciful forms "meese" and "mongeese", or the form "mie" in the couplet "A cube of cheese no larger than a die, may bait the trap to catch a nibbling mie" (Ambrose Bierce, attributed to "that eminent poet and domestic economist, Senator Depew".)

Solution 2:

In this case I would choose "Bigfoots." As in, "Three Bigfoots were spotted in the Sierra Nevada mountains over the weekend."

If you say it the other way, it is confusing: "Three Bigfeet were spotted...."