jigger, n.⁴ — Green’s Dictionary of Slang

jigger n.⁴

[? jigger n.¹ or jigger n.⁵ (1) or SE jig, to move up and down]

1. the penis.

1890–1904

2. the vagina.

1890–1904		Farmer & Henley Sl. and Its Analogues.
1935		in G. Legman Limerick (1953) 193: Her belly began to rise, / And out of her jigger / Jumped a cast-iron nigger.
1941		in Randolph & Legman Ozark Folksongs and Folklore (1992) I 133: Learned from a Negro in central Arkansas, about 1910. [...] ‘Went upstairs to get a little jigger, / She says wait till the hole gets bigger, um-hum’.