The gramatically 'correct' way of saying 'Mudda cunt' i.e. it's really supposed to be "Mudda's cunt" but for convenience the apostrophe is omitted.
Initially used as an even ruder, cruder and lewder way of insulting one (by insulting one's mother).
Probably derived from "yo mamma" jokes.
Considered VERY degrading.
But now it is used in common parlance very loosely i.e. appropriate for use in any and every sentence.
"Windale muddas cunt"
"Where is my muddas cunt pen?"
hits foot "OHhh muddas cunt!!!"
confused, frustrated "What the muddas cunt!?!?!??"