Green’s Dictionary of Slang

almond n.¹

the penis.

1893		J. Tabrar [perf. Marie Lloyd] Buy Me Some Almond Rock 🎵 I shall say to a young man gay / If he treads upon my frock / Randy Pandy, sugardy candy / Buy me some Almond Rock.
1960		J. Franklyn Dict. of Rhy. Sl. 32/1: almond rock Cock (penis) 19C. Generally reduced to almond.
1969		S.T. Kendall Up the Frog.
1980		Maledicta IV:2 (Winter) 193: The grocery, the butcher’s and the sweet shop are all represented as well as the greengrocer’s. Thus there is almond (-rock = rhyming slang on cock).
1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: almond n. 1. Penis. From the rhyming slang, almond rock – cock. 2. An imperial measure of semen; approximately one stomach full.