Green’s Dictionary of Slang

(Scot./Irish juv.) utterly filthy.

1872		Daily Gaz. for Middlesborough 13 Feb. 3/6: Foul were the roads, and fou’ the dubs, [...] A’ clatty.
[1916		L. Pound ‘Word-List From Nebraska’ in DN IV:iv 273: clatty, adj. Mussy, slovenly [...] ‘You are such a clatty dishwasher’].
1973		(con. mid-1960s) J. Patrick Glasgow Gang Observed 231: Clatty – ‘stourie’, ‘dirty’, ‘manky’.
1983		W.F Marshall ‘Me an’ Me Da’ in Livin’ in Drumlister 32: An’ if me shirt’s a clatty shirt / The man to blame’s me da.
1996		(ref. to 1963) D. Healy Bend for Home 135: The shit smell from the clatty toilets seeped through the disinfectant.
2001		OnLine Dict. of Playground Sl. 🌐 clatty adj. exceptionally dirty, the most disgusting level of dirt imaginable. Usually referred to an item. e.g. ‘that’s pure clatty’, or a person e.g. ‘By Christ, he’s a clatty bastard’.