watch

{{11}}watch (n.) O.E. wæcce "a watching," from wæccan (see WATCH (Cf. watch) (v.)). Sense of "sentinel" is recorded from c.1300; that of "person or group officially patroling a town (esp. at night) to keep order, etc." is first recorded 1530s. Meaning "period of time in which a division of a ship's crew remains on deck" is from 1580s. Sense of "period into which a night was divided in ancient times" translates L. vigilia, Gk. phylake, Heb. ashmoreth.

The Hebrews divided the night into three watches, the Greeks usually into four (sometimes five), the Romans (followed by the Jews in New Testament times) into four. [OED]

The meaning "small timepiece" is from 1580s, developing from that of "a clock to wake up sleepers" (mid-15c.).

{{12}}watch (v.) O.E. wæccan "keep watch, be awake," from P.Gmc. *wakojan; essentially the same word as O.E. wacian "be or remain awake" (see WAKE (Cf. wake) (v.)); perhaps a Northumbrian form. Meaning "be vigilant" is from c.1200. That of "to guard (someone or some place), stand guard" is late 14c. Sense of "to observe, keep under observance" is mid-15c. Related: Watched; watching.