Someone who tells on others, especially to authority figures like teachers or police; also means to steal something quickly.
Origin unclear, possibly from Yiddish 'snitsh' or Dutch. First appeared in English in the 1700s meaning a nose (because informants stick their nose into others' business), later came to mean an informant, and eventually also acquired the meaning of petty theft.
The word 'snitch' perfectly captures how informants were viewed—as people sticking their 'nose' (the literal meaning) into everyone else's business, which is why the slang stuck around for centuries!
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