Green’s Dictionary of Slang

(orig. Scot.) to stink; in fig. use, to be very unattractive.

1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: ming Scotch v. To emit a foul smell. As in: ‘Christ, it’s minging in here!’.
2003		N. Griffiths Stump 154: Christ that fuckin mings [...] It smells like fresh shit.
2018		I. Welsh Dead Man’s Trousers 116: Ah hate tae be a cunt, but he kind ay fuckin mings.