Feces or excrement; also used as a vulgar interjection expressing anger, surprise, or frustration, or as a verb meaning to defecate.
From Old English 'scitan' and Proto-Germanic 'skitan,' related to 'skid' and 'shot'; the word originally had no taboo status but became vulgar over time as society developed standards around bathroom language.
Most 'four-letter words' are actually ancient Anglo-Saxon words that survived while their fancy Latin equivalents ('feces,' 'defecate') were imported later—which is why swearing in English feels like you're speaking your most primal language.
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