The Existence of the Word "Unutilably"

Probably not quite the right place to ask but I decided to give this sub-reddit a try just in case I read it in something quite obscure or old.

I swear I've read this word multiple times in books from legit authors and publishers, but I can't find a single instance of it on Google, in articles or online dictionaries. I found one instance of "Unutilable" being used in a legal context but I can't find Dictionary entries for that either. Any help is greatly appreciated. There must be some pretty clever people in here.