The parts of a shirt or jacket that cover the arms; or the cardboard covers for vinyl records.
From Old English 'slyfe,' related to 'slip.' Originally meant something that slips on. The record album meaning emerged in the 1940s when sleeve-like covers protected vinyl.
Vinyl record 'sleeves' kept their name even though digital files never had physical sleeves—so Spotify albums still have 'cover art' and music industry still talks about 'album sleeves' from a technology that's nearly obsolete!
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