Green’s Dictionary of Slang

1. (US black) a petite, (young) woman.

1941

‘Digg Mee’ ‘Observation Post’ in N.Y. Age 28 June 9/7: Virginia Goff, the fickle little ditty, has once more taken her heart down the city [ibid.] 9/6: He brought a lovely little female ‘ditty’ [...] of course wifie doesn’t know.

2. (US campus) a small object; a penis.

1971		K. Gilbert Cherry Pickers III ii: How’s yer ditty [...] How’s ya knackers?
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Ditty (noun) Anything, especially a small trinket, an object, a penis.