Don't get me wrong, I am on the boat of thinking it's a kitsune/tanuki zoan and I get that it's to big of a coincidence to have that epithet and have magical powers of the disguising nature (so far that's all we've seen him use), but I'm still thinking it's too soon to rule out that possibility just yet.
@Noqanky: I believe you do recall correctly about the tail not being able to be disguised, whether he would always have it is another question because his DF is still a mystery. I've read arguments about whether or not he'd be able to use his powers without some kind of transformation (I disagreed with that… I think he would)..
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This theory is really stupid and unlikely, so don't go into a rage about how wrong it is...
Personally, I like the the name "Kinemon the Will o' Wisp" (which is the translation I read from mangarule)...
The meaning of it has to do with a ghostly light guiding travelers with a safe passage, in most cases they've been swamp/marsh related, and it's been proven that it was in fact "marsh gas" that can spontaneously catch fire when in contact with air..After reading that part it reminded me of when Zoro mentioned that he wanted a fire sword and got me wondering that perhaps Kinemon got that epithet from his abilities in sword fighting, whether it's due to his devil fruit or not he probably uses fire related attacks/makes his sword ..A fire sword...Which if and when Zoro saw that, he'd flip shit to say the least..
Edit: Hachi had substance, it's just to bad that he was weak and Oda had planned for another fishman to join. Kinemon just has so much more though, I havn't been this into a newly introduced character since Brook.