1660s, from watch (n.) in the "timepiece" sense + work (n.).
Entries linking to watch-work
watch n.
Old English wæcce "a watching, state of being or remaining awake, wakefulness;" also "act or practice of refraining from sleep for devotional or penitential purposes;" from wæccan "keep watch, be awake," from Proto-Germanic *wakjan, from PIE root *weg- "to be strong, be lively."
From c. 1200 as "one of the periods into which the night is divided," in reference to ancient times translating Latin vigilia, Greek phylake, Hebrew ashmoreth. From mid-13c. as "a shift of guard duty; an assignment as municipal watchman;" late 13c. as "person or group obligated to patrol a town (especially at night) to keep order, etc."
Also in Middle English, "the practice of remaining awake at night for purposes of debauchery and dissipation;" hence wacches of wodnesse "late-night revels and debauchery." The alliterative combination watch and ward preserves the old distinction of watch for night-time municipal patrols and ward for guarding by day; in combination, they meant "continuous vigilance."
Military sense of "military guard, sentinel" is from late 14c. General sense of "careful observation, watchfulness, vigilance" is from late 14c.; to keep watch is from late 14c. Meaning "period of time in which a division of a ship's crew remains on deck" is from 1580s. The meaning "small timepiece" is from 1580s, developing from that of "a clock to wake up sleepers" (mid-15c.).
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]
On þis niht beð fowuer niht wecches: Biforen euen þe bilimpeð to children; Mid-niht ðe bilimpeð to frumberdlinges; hanecrau þe bilimpeð þowuene men; morgewile to alde men. [Trinity Homilies, c. 1200]
work n.
Old English weorc, worc "something done, discrete act performed by someone, action (whether voluntary or required), proceeding, business; that which is made or manufactured, products of labor," also "physical labor, toil; skilled trade, craft, or occupation; opportunity of expending labor in some useful or remunerative way;" also "military fortification." This is from Proto-Germanic *werka- "work" (source also of Old Saxon, Old Frisian, Dutch werk, Old Norse verk, Middle Dutch warc, Old High German werah, German Werk, Gothic gawaurki), from PIE *werg-o-, a suffixed form of the root *werg- "to do."
The meaning "physical effort, exertion" is from c. 1200; that of "scholarly labor" or its productions is from c. 1200; the meaning "artistic labor" or its productions is from c. 1200. The sense of "labor as a measurable commodity" is from c. 1300. The meaning "embroidery, stitchery, needlepoint" is from late 14c.
Work of art attested by 1774 as "artistic creation," earlier (1728) "artifice, production of humans (as opposed to nature)." Work ethic recorded from 1959. To be out of work "unemployed" is from 1590s. To make clean work of is from c. 1300; to make short work of is from 1640s.
Proverbial expression many hands make light work is from c. 1300. To have (one's) work cut out for one is from 1610s; to have it prepared and prescribed, hence, to have all one can handle. Work in progress is from 1930 in a general sense, earlier as a specific term in accountancy and parliamentary procedure.
Work is less boring than amusing oneself. [Baudelaire, "Mon Coeur mis a nu," 1862]