A mispronunciation for ganache, a form of dark semi sweet chocolate blended with cream. Used by ignorant people who don't know that the pronunciation sounds like g'nosh
"Hey, whos giannaisthekoolest? Why does she have such a weird sense of humor?"
'Oh, shes a amazing person and such a great friend! You should definitely get to know her! Her sense of humor is amazing! She always makes me laugh :D'