Old English weorc, worc "something done, deed, action, proceeding, business, military fortification," from Proto-Germanic *werkan (cf. Old Saxon, Old Frisian, Dutch werk, Old Norse verk, Middle Dutch warc, Old High German werah, German Werk, Gothic gawaurki), from PIE root *werg- "to work" (see urge (v.)).
In Old English, the noun also had the sense of "fornication." Workhouse in the sense of "place where the poor or petty criminals are lodged" first appeared 1650s. Works "industrial place" (usually with qualifying adj.) is attested from 1580s. Work ethic recorded from 1959.