Plural of pane; individual sections of glass in a window or door, usually separated by frames or muntins.
From Old French 'pane' (cloth panel), from Latin 'pannus' (cloth/rag). The word shifted from describing cloth sections to glass sections because both were arranged in rectangular frames.
A window pane was originally just a piece of cloth like a panel—the name stuck around when people started using glass, because both served the same purpose of dividing spaces!
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