When words are mispronounced or substituted for similar sounding words by accident; similar to malapropisms.
Originates from PC World, Croydon, England, 2011.
James: Something cheap as I have a really good deal right now.
Salesman: Oh really, what deal are you on?
James: Well, at the minute I pay five pounds a munch.
*Salesman and other customers snigger and chortle*
James: A month! Five pounds a month!
Well aren't you being a munch!