Green’s Dictionary of Slang

1. of a woman, very attractive.

1891

‘’Arry on Wheels’ in Punch 7 May 217/2: We couldn’t ’elp doing a larf, though the gurl was pertikler yum-yum.

2. sexually provocative.

1878		‘’Arry on Pooty Women’ in Punch 21 Sept. in P. Marks (2006) 149: The Swellesses likes to be looked at in attitoods yum-yum.
1914		Sport (Adelaide) 4 Dec. 5/6: Sport wants to know when Maggie G will put on her war paint and sally forth on the yum-yum trail again.

3. deliciously pleasurable.

1883		‘’Arry at the Royal Evening Fête’ in Punch 28 July 38/2: And a Duchess to draw him his bitter comes awfully yum-yum too.
1885		Bulletin (Sydney) 25 July 13/1: So the dear little things were incontinently packed off to an Orphan Asylum, and yum-yum happiness was the reward of the loving pair.
1913		E.L. Warnock ‘Terms of Approbation And Eulogy’ in DN IV:i 24: yum-yum. First rate, excellent. [...] That candy’s yum-yum.
1913		‘Lord Ballyrot in Slangland’ in Tacoma Times (WA) 21 Aug. 4/4: You want to show your dairy girl a grand time by handing her a young trunk of yum-yum tablets.
1928		V. Hurst Big Game 110: ‘You’re positively yum-yum,’ Dan whispered.
1934		(con. 1920s) J.T. Farrell Young Manhood in Studs Lonigan (1936) 159: I hear the hustlers are yum-yum in France, too.
1972		Loydie & the Lowbites [song title] Yum Yum Pussy Yum Yum Yum .
1986		E. Weiner Howard the Duck 52: Want itty-bitty yum-yum candies?