Green’s Dictionary of Slang

dingle-dangle n.

the penis.

1937–84		Partridge DSUE (1984) 310/2: from ca. 1895.
1938		‘Justinian’ Americana Sexualis 20: The membrum virile [...] dingle-dangle.
1964		J. Thompson Pop. 1280 in Four Novels (1983) 393: Probably you ain’t got as a long a dingle-dangle as he has – they tell me them idjits are hung like a stud-hoss.
1975		(con. 1930s) H. Anderson Men of the Milford Road 128: ‘He’s scratching what?’ asked the woman. ‘His dingle-doodle,’ said Sam without batting an eyelid [...] ‘His dingle-doodle – you know – his doodle dasher.’.