Green’s Dictionary of Slang

babu n.

also baboo
[Hind. babu, a term of respect (Mr, Esquire) or an educated man]

1. (also baboo-boy) an old East Indian man, usu. bearded and poor.

[[Ind]J.W. Kaye Peregrine Pultuney II 56: He hailed a very respectable looking stout old Baboo].
[US]E. Walrond Tropic Death (1972) 136: ‘A grave? Mercy! For whom?’ [...] ‘Fo’ de baboo wha’ chop arf ’im wife head, mum.’ [Ibid.] 142: The baboos, behind pots of rotie and callaloo.
[UK]R. Antoni Grandmother’s Erotic Folktales 11: One of the little baboo-boys came running with a map.

2. (also babu-man) an ugly old man.

[WI]Allsopp Dict. Carib. Eng. Usage.

3. (also babu-man) an imaginary figure, ugly and old, conjured up to frighten children.

[WI]Allsopp Dict. Carib. Eng. Usage.