Green’s Dictionary of Slang

the genitals, of either sex; thus the coarse query, How’s your rhubarb, Missus?

1870		Cythera’s Hymnal 58: ‘From the state that my rhubarb is in, / I am sure that my beast of a brother, / Is going now to have a put in’.
1936		in Randolph & Legman Ozark Folksongs and Folklore (1992) I 417: Well, the cat couldn’t kitten an’ the slut couldn’t pup, / (And) the old man couldn’t get his rhubarb up.
1956		N. Algren Walk on the Wild Side 203: Cat had a kitten, kitten had a pup / [...] / Say old man is your rhubarb up?
1966		Trimble 5000 Adult Sex Words and Phrases.
1980		Maledicta IV:2 (Winter) 193: The fourth compartment contains those words already discussed as of limited usage – bananas and rhubarb.
1989		H. Rawson Dict. of Invective (1991) 327: rhubarb. [...] a symbol for the genitals, usually male.
1992		Randolph & Legman Ozark Folksongs and Folklore I 325: This is all so well known in the Ozarks that the word rhubarb – which also means penis there [...] is not to be pronounced before ‘decent’ women’.
2024		J. Meades Empty Wigs (t/s) 285: He was such a gal sneaker... he so loved to pull his rhubarb out... encourage the gels to help it swell..