It is an "error", but it applies almost exclusively to speech, to pronunciation; very rarely and by extension to writing. It is not a synonym for mistake, let alone "fatal". It comes from the French fourcher ("to get tangled, to get stuck [like noodles on a fork]"). See furcia , saraza , gazapo ( error ) , errata , lapsus linguae .
The question induces to error: I personally do the consultation on the concept of Furcio...And it repregunta on another meaning and which pretendi found in his great dictionary... is not understandable in any chance oi a reference that he had made a mistake someone and said cometi a furcio - now if Furcia, Fig fem. is a disparaging of prostitute... well we could in the male prostitute fig. call MASC.Al Furcio.
