Green’s Dictionary of Slang

mong-mong n.

[pron. of Carib.E. Mount St Moritz Bajan, a poor white one of whose ancestors moved to the Grenadan estate of St Moritz c.1870s, working as a market gardener]

(W.I., Gren.) a poor white.

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