Old English widewe, wuduwe, from Proto-Germanic *widuwō (source also of Old Saxon widowa, Old Frisian widwe, Middle Dutch, Dutch weduwe, Dutch weeuw, Old High German wituwa, German Witwe, Gothic widuwo), from PIE adjective *widhewo (source also of Sanskrit vidhuh "lonely, solitary," vidhava "widow;" Avestan vithava, Latin vidua, Old Church Slavonic vidova, Russian vdova, Old Irish fedb, Welsh guedeu "widow;" Persian beva, Greek eitheos "unmarried man;" Latin viduus "bereft, void"), from root *uidh- "to separate, divide" (see with).
Extended to "woman separated from or deserted by her husband" from mid-15c. (usually in a combination, such as grass widow). As a prefix to a name, attested from 1570s. Meaning "short line of type" (especially at the top of a column) is 1904 print shop slang. Widow's mite is from Mark xii.43. Widow's peak is from the belief that hair growing to a point on the forehead is an omen of early widowhood, suggestive of the "peak" of a widow's hood. The widow bird (1747) so-called in reference to the long black tail feathers of the males, suggestive of widows' veils.