[ult. cauliflower n.2 (1); ‘A woman, who was giving evidence in a case wherein it was necessary to express those parts, made use of the term cauliflower, for which the judge on the bench, a peevish old fellow, reproved her, saying she might as well call it an artichoke. Not so, my lord, replied she, for an artichoke has a bottom, but a **** and a cauliflower have none’ (Grose 1785)]
[late 18C–19C] the vagina.
[19C; 1990s+] sexual intercourse.
do a bit of cauliflower
[late 19C–1910s; 1990s+] to have sexual intercourse.