Mongo: A discarded item that is picked up, retrieved, and rescued. Also used as a verb: to pick up garbage for the purpose of redeeming it.
From "Dr. Garbage," Ben McGrath's 2006 New Yorker feature about Robin Nagle, anthropologist in residence with New York City's Department of Sanitation:
Nagle’s interests lie more with the trash collectors than with the
trash, although the two intersect on the subject of “mongo”—sanitation
lingo for “redeemed garbage” or the act of collecting it. (Nagle
consulted a lexicographer, looking for help in tracking down the
etymology, to no avail.) “Within the department, if you mongo or if you
don’t—there’s kind of a dividing line,” she said. “ ‘He mongos.’ ‘Do
you mongo?’ ‘Oh, mongo, are you kidding? I wouldn’t mongo.’ ” She
paused. “Hell, I mongo, absolutely. And I have some pretty nice things.”
Mongo is the first word to be considered in Slang: The People's Poetry, the new book by Indiana University English professor Michael Adams. (Adams is also the author of Slayer Slang: A Buffy the Vampire Slayer Lexicon.) Here's the book's opening paragraph:
If I were to say to you right now, "Dude, I know where we can score some phat mongo," what would you do? Would you call the police? Would you come along to see what I meant by mongo? Would you look up mongo in the dictionary before we left, so that you knew what you were getting into? I mean, what kind of word is mongo? It doesn't sound like an English word. It certainly isn't a word you learned by studying for vocabulary quizzes in school. Is it a bad word for something good, or a good word for something bad?
Adams traces the popularization of mongo to a 2004 book by Ted Botha, Mongo: Adventures in Trash. But, he adds:
Mongo isn't a new word; the Historical Dictionary of American Slang ... records it from 1984, and rumor has it that the word had been around for at least a decade by then. Indeed, Grant Barrett, in The Official Dictionary of Unofficial English (2006), reports that "evidence from the unpublished Lexicon of Trade Jargon, compiled by the [Depression-era] Works Progress Administration, has a form of this word from before 1983, mungo, referring to the person who salvages discarded items, rather than the things being salvaged."
More citations for mongo are at Word Spy. None of them mentions the Cuban percussionist Mongo Santamaria, whose name was used in a pun in the Mel Brooks film Blazing Saddles ("Mongo! Santa Maria!").
By the way, I thoroughly enjoyed Slang: The People's Poetry, which showed up one day on my doorstep courtesy of the generous folks at Oxford University Press. It's a freewheeling yet scrupulously researched amble through the worlds of (for example) Cockney rhyming slang, 19th-century slang in Louisa May Alcott's Little Women, drug slang (Ecstacy, or MDMA, goes by e-mail, Kleenex, gum, wafer, and clarity, to name but a few synonyms), snowboarding jargon, and the fake African-American slang taught to clueless manager Michael Scott in the American TV series The Office. (Authentic African-American slang takes up a large portion of one chapter.) There's a long and fascinating discussion of the various slang meanings of morning glory, and a spirited consideration of Flandersisms like okelly dokelly in The Simpsons ("Lexifabricography and the Lexically Meaningful Infix").
And my vocabulary is greatly enriched by the addition of lochrity, a Scottish slang term meaning "the condition of having many lakes."