cross-hair (n.)youdaoicibaDictYouDict[cross-hair 词源字典]
also crosshair, cross-hairs, 1755, of a telescope, 1780 in gunnery, from cross- + hair (n.). Also often in early 19c. spider-line, spider's-line (1819).[cross-hair etymology, cross-hair origin, 英语词源]