Green’s Dictionary of Slang

(UK Und./Scot.) a fool, an incompetent.

1988		M. Munro The Patter—Another Blast.
1999		D. Ross Xenophobe’s Guide to the Scots 16: One feeble utterance can mark a person down as a brainless ‘numpty’ for life.
2004		C. Brookmyre Be My Enemy 114: It [i.e. a joke] was a sheer belter because it illustrated that [...] Rory could also be a blundering numpty.
2007		N. ‘Razor’ Smith Raiders 246: Giving a gun to some numpty who might shoot his own foot off [...] is a no-no.
2009		N.Y. Times q. in Twitter: 9 Sept. 2019 🌐 Boston’s Kenmore Square [...] was home to three-card-monte men, ordinary punks, beer-devastated Red Sox bleacher-seat numpties,.
2010		Sun. Times 19 Dec. 5/1: I had expected nothing less of the leader of the world’s numptiest radicals.
2011		S. Kelman Pigeon English 100: Your sister’s a numptie, man. She thinks she’s a chicken.
2016		Times 29 June 🌐 [Corbyn] gets his revenge by looking like an utter numpty? Funny kind of revenge.
2019		Twitter 9 Sept. 🌐 You mean The GOP in America licking Numpty’s [i.e. Donald Trump] arsehole.