Demonfucious is a word that Waluigi created to describe his mustache. This is because his mustache is so ƒ#ç%!%© sharp it could poke your ƒ#ç%!%© eye out! You may think that Demonfucious is a Demonic version of Confucius, but, really, it's something that's so sharp and bad@$# that it can poke your ƒ#ç%!%© eye out!
Noone knows why Waluigi calls his mustache "Demonfucious." Waluigi himself doesn't know. Oh well, he was probably just drunk or something.