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early 13c., literally "wind eye," from Old Norse vindauga, from vindr "wind" (see wind (n.1)) + auga "eye. (see eye (n.)). Replaced Old English eagþyrl, literally "eye-hole," and eagduru, literally "eye-door."
Originally an unglazed hole in a roof, most Germanic languages adopted a version of Latin fenestra to describe the glass version, and English used fenester as a parallel word till mid-16c. Window dressing is first recorded 1790; figurative sense is from 1898. Window seat is attested from 1778. Window-shopping is recorded from 1922. Window of opportunity (1979) is from earlier figurative use in U.S. space program, e.g. launch window (1965).
window win·dow (wĭn'dō)
[modeled on the winding down of a clock or other machine]
properly only an opening in a house for the admission of light and air, covered with lattice-work, which might be opened or closed (2 Kings 1:2; Acts 20:9). The spies in Jericho and Paul at Damascus were let down from the windows of houses abutting on the town wall (Josh. 2:15; 2 Cor. 11:33). The clouds are metaphorically called the "windows of heaven" (Gen. 7:11; Mal. 3:10). The word thus rendered in Isa. 54:12 ought rather to be rendered "battlements" (LXX., "bulwarks;" R.V., "pinnacles"), or as Gesenius renders it, "notched battlements, i.e., suns or rays of the sun"= having a radiated appearance like the sun.