Too interested in other people's business; prying into things that aren't your concern.
From 'nose' with suffix '-y,' created around the 1800s. The logic is that a nosy person 'sticks their nose into' others' affairs. The visual image of someone physically poking their nose into things made this a perfect descriptive word.
Nosy people 'stick their nose in'—the word literally describes the action that best represents meddling. Dogs are naturally nosy (their noses lead them everywhere), and the word works for curious humans the same way.
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