clanger, n.¹ — Green’s Dictionary of Slang

clanger n.¹

[the ‘noise’ of (1) its ‘hitting the ground’, (2) the testicles 'clanging together’]

1. a mistake, esp. a social solecism.

1948		Lawrentian (St. Lawrence Coll., Ramsgate) Easter 8: Clanger. A peculiarly heavy brick... Prefects lead the way in dropping these objects [OED].
1963		G. Lambert Inside Daisy Clover (1966) 219: It was a clanger even for Gloria.
1985		J. Wambaugh Secrets of Harry Bright (1986) 47: You like real clangers?
1999		Guardian 14 May 30: Last year’s award to Dwight Yorke really has turned out to be a clanger.
2015		L. McInerney Glorious Heresies 91: Jimmy [...] drew Tony Cusack’s indiscretion from catastrophe to conspiracy to clanger.

2. (Aus.) in pl., the testicles.

1999

P. Temple Black Tide (2012) [ebook] Stable wants his clangers on a plate.

drop a clanger (v.)

to make a social error, the awfulness of which reverberates around the assembled gathering.

1945		Lethbridge (Alberta) Herald 17 Nov. 10/3: Ma and Pa, if they don’t want to drop a clanger, will also have to beeze up on their English with the following glossary [...].
1953		A. Buckeridge Jennings’ Diary 201: You haven’t half dropped a clanger with Old Wilkie.
1968		Sun. Times 26 Apr. 34: He has good reason for embarrassment for the Americans seemed to have dropped a fair sized clanger.
1988		Beano Comic Library No. 146 24: Come out, the pupil who dropped a clanger!
2000		Indep. on Sun. 12 Mar. 12: Harvey Nicks drops a clanger with ‘fat’ ads.
2006		B. Matthews Intractable [ebook] Then Carol [Thatcher] dropped a clanger.