Green’s Dictionary of Slang

(US juv.) the penis; thus pound one’s peenie v., to masturbate.

1943		in G. Legman Limerick (1953) 50: A wonderful tribe are the Sweenies, / Renowned for the length of their peenies.
1966		(con. 1958) R. Farina Been Down So Long (1972) 43: Wonder will his penie calcify, break off?
1972		B. Rodgers Queens’ Vernacular 50: the penis [...] peeny.
2004		Eble Campus Sl. Apr. 5: peen – penis.
2013		nsfwcorp.com 9 Jan. 🌐 To whatever voice in your head that feels guilty for touching your peen, I say fuck you.
2023		Twitter 19 Apr. 🌐 First thing: small peen Greg’s sweats look like he piddled in them.