PIE*wegから、丈夫な、活力のある、語源的にはvegetable, wakeと同じ、派生的にwatch over, look after, 比較するためにtを挿入する、bake, batch, make, watch.
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]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."
On tis niht bee fowuer niht wecches: Biforen euen te bilimpee to children; Mid-niht ee bilimpee to frumberdligges; hanecrau te bilimpee towuene men; morgewile to alde men. [Trinity Homilies, c. 1200]