Green’s Dictionary of Slang

crazy, insane, eccentric.

1911		Daily Trib. (Bismarck, ND) 27 Oct. 4/3: With a ding-a-ling hat, / And gowns that dismay / And remarks that fall pat / in the slang of the day.
1935		A.J. Pollock Und. Speaks 31/1: Ding-a-ling, brainless.
1970		Playboy Aug. 37: How do I handle [...] her utterly ding-a-ling sex views? [HDAS].
1975		J. Wambaugh Choirboys (1976) 31: I think he’s got a leaky seabag. Dingaling. Psycho. You can’t even talk to him.
1999		Guardian Guide 26 June–2 July 11: Rumours of him going completely ding-a-ling might not be too wide of the mark.