means A short coat that covers the upper body, worn for warmth or style, or by extension the outer covering of something like a book or a wire.

from From Old French 'jaquet,' a diminutive of 'jaque,' a kind of short, close-fitting peasant tunic. The 'jaque' itself is often linked to 'Jacques,' the generic French nickname for a common man (think how we say 'every Tom, Dick, and Harry') — so a jacket was, in a sense, the everyman's little coat. That said, some trace it instead to Spanish 'jaco' or to a word for chainmail; the trail gets muddy, so the 'Jacques' story, while popular and charming, is best held loosely.