biv·ou·ac / ˈbivoōˌak; ˈbivwak/ • n. a temporary camp without tents or cover, used esp. by soldiers or mountaineers.• v. [intr.] (-acked, -ack·ing) stay in such a camp: he'd bivouacked on the north side of the town the battalion was now bivouacked in a field.ORIGIN: early 18th cent. (denoting a night watch by the whole army): from French, probably from Swiss German Bîwacht ‘additional guard at night,’ apparently denoting a citizens' patrol supporting the ordinary town watch.

bivouac (orig.) night-watch under arms; (hence) temporary encampment without tents. XVIII. — F. bivouac — MLG. biwacht or Du. bijwacht lit. ‘extra watch’.
Hence as vb. XIX.

bivouac See DORYLINAE.