Green’s Dictionary of Slang

bumbo n.2

[bum n.1 and/or Fante bumbo, vulva, but note Efik mbumbu, rotten, putrefied, decomposed; orig. W.I. use, where the term is also used to mean SE alligator; thus suggesting poss. vagina dentata imagery]

1. [mid-18C+] (also bombo-red) the vagina.

2. [mid-19C+] the buttocks, the anus.

In compounds

bumborass (adj.)

[2010s] (W.I.) non-specific intensifier used as adj.