Green’s Dictionary of Slang

dummy n.3

[its silence or its use for sucking on]

the penis.

[UK]Romance of Lust 127: Patting it with her hand, she said – ‘Ah! my dear little dummy.’.
[US]Monteleone Criminal Sl. (rev. edn).
[US]S. Bellow Augie March (1996) 86: So take my advice and don’t play with your dummy.
[US]Wentworth & Flexner DAS.
[US]T. Berger Sneaky People (1980) 161: Sometimes he went at it so ardently in bed, despite the rubber, the head of his little dummy was chafed.

In phrases

beat one’s/the dummy (v.) (also cuff one’s/the dummy, flog one’s dummy, whip...)

to masturbate; thus dummy flogger n., a masturbator.

[US]J. Conroy World to Win 40: If you don’t quit floggin’ yer dummy, the undertaker’s gonna have a job.
[US] in G. Legman Limerick (1953) 276: There was a young fellow named Rummy / Who delighted in whipping his dummy.
[US]Goldin et al. DAUL 25/1: Beat the dummy or pup. (P) To masturbate.
[US]Kerouac letter 10 Dec. in Charters II (1999) 89: Don’t flog your dummies, and save some girls for me.
[US]Trimble 5000 Adult Sex Words and Phrases.
[US]T. Berger Sneaky People (1980) 93: ‘Should I go right now?’ ‘Well, I think so,’ the butcher said, winking, ‘unless you want to go in the icebox and beat your dummy.’.
[US]J. Wambaugh Choirboys (1976) 130: He had become tired of being dragged off to jail every time he got a little bit drunk and flogged his dummy on the porch.
[US]E. Folb Runnin’ Down Some Lines 229: beat the dummy Masturbate.
[US]J. Wambaugh Glitter Dome (1982) 160: I like underwear too, but I try to control some bad habits: Polaroids, bookmakers, flogging your dummy.
[US]J. Wambaugh Lines and Shadows 257: Blood drinkers, gerontological dummy floggers. They had them all.
[US]J. Wambaugh Secrets of Harry Bright (1986) 61: The theatre manager, who was sick and tired of dummy floggers chasing off legitimate customers.
[US]Bentley & Corbett Prison Sl. 63: Flog the Log Masturbation. (Archaic: beat the dummy).
[UK]Roger’s Profanisaurus 3 in Viz 98 Oct. 9: cuffing the dummyv. US. mil. Wanking See scrubbing the cook.