embrasure (n.)youdaoicibaDictYouDict[embrasure 词源字典]
"enlargement of the interior aperture of a door or window," 1702, from French embrasure (16c.), from Old French embraser "to cut at a slant, make a groove or furrow in a door or window," from assimilated form of en- "in" (see en- (1)) + braser "to cut at a slant."[embrasure etymology, embrasure origin, 英语词源]