Well, IMO names of anything should be allowed, the limit being as long as it isn't a word you made up, or at least is a word that SOME people have heard of. People have guessed people names, and Pokemon names, and place names, and other proper nouns. I wouldn't reccomend using it as THE word, but its not really that bad. But for guesses, their perfectly acceptable... so I guess they can be acceptable for THE word. Preferrably not, though... but if you're confident, go ahead.

Jujutsu is my next guess.

~Zak