A somewhat out-of-date word, but it seems useful still. The forking can be either literal, as in a snake's tongue, or metaphoric as in the idiom for speaking with a forked tongue like a duplicitous rat-bastard. Not that I'm bitter. This is an English compound made from Latin roots, from fissus, the past participle of findere, to split + lingual, from Medieval Latin linguālis, of or pertaining to the tongue or languages, from Latin lingua, tongue (and which ultimately is a cognate -- the Old Latin form was dingua).
Frankly, the creepiest band member is that fissilingual drummer -- gives me the creeps when he screams.