for a very long or indefinitely long time
He stayed out until the cows came home.
Old English cu "cow," from Proto-Germanic *kwon (cf. Old Frisian ku, Middle Dutch coe, Dutch koe, Old High German kuo, German Kuh, Old Norse kyr, Danish, Swedish ko), earlier *kwom, from PIE *gwous (cf. Sanskrit gaus, Greek bous, Latin bov-, Old Irish bo, Latvian guovs, Armenian gaus "cow," Slovak hovado "ox"), perhaps ultimately imitative of lowing (cf. Sumerian gu, Chinese ngu, ngo "ox"). In Germanic and Celtic, of females only; in most other languages, of either gender. Other "cow" words sometimes are from roots meaning "horn, horned," e.g. Lithuanian karve, Old Church Slavonic krava.
"intimidate," c.1600, probably from Old Norse kuga "oppress," of unknown origin, but perhaps having something to do with cow (n.) on the notion of easily herded. Related: Cowed; cowing.
A cow and her calf were not to be killed on the same day (Lev. 22:28; Ex. 23:19; Deut. 22:6, 7). The reason for this enactment is not given. A state of great poverty is described in the words of Isa. 7:21-25, where, instead of possessing great resources, a man shall depend for the subsistence of himself and his family on what a single cow and two sheep could yield.