A Talk of the Town piece in the issue of the New Yorker for 13 November 2006 reported on an anthropologist-in-residence programme in the city’s Department of Sanitation. An aside mentioned mongo, a word used by sanitation workers for the act of creatively recycling refuse, reclaiming and putting back to useful purpose items that had been thrown out. The magazine has featured the word before — its first recorded appearance was in the New Yorker in September 1984.
It’s one of that large group of terms which is almost impossible to research and about whose origin nobody seems to know anything at all. But we may with some confidence assume that it’s not the same word as the US slang term mongo meaning “huge” (which is a short form of humongous, perhaps influenced by mondo) or “idiot” (which is an abbreviation of Mongol or mongoloid, in the now deeply deprecated sense of a sufferer from Down syndrome), nor that it refers to the Flash Gordon planet.
It matches least badly to mungo, another name for shoddy, an inferior cloth made from recycled fibres taken from old woven or felted material. The Oxford English Dictionary points in turn, very cautiously, to the origin of that in mung for “a mingling, a mixture, a confusion, or a mess” (a definition that ought to be set to music, it has such rhythm); in turn this may be from ymong, a company of people, which is a precursor of among. The OED retells an old tale that tried to explain mungo: when the first sample of the cloth was made, a Yorkshire foreman said “It won’t go” (it’s inadequate, it won’t fill the need), to which the master replied “But it mun go” (it must go).