Why is the ninth month called September?
Old English wif "woman," from Proto-Germanic *wiban (cf. Old Saxon, Old Frisian wif, Old Norse vif, Danish and Swedish viv, Middle Dutch, Dutch wijf, Old High German wib, German Weib), of uncertain origin. Dutch wijf now means, in slang, "girl, babe," having softened somewhat from earlier sense of "bitch."
Some proposed PIE roots include *weip- "to twist, turn, wrap," perhaps with sense of "veiled person" (see vibrate); or *ghwibh-, a proposed root meaning "shame," also "pudenda," but the only examples of it are wife and Tocharian (a lost IE language of central Asia) kwipe, kip "female pudenda."
The modern sense of "female spouse" began as a specialized sense in Old English; the general sense of "woman" is preserved in midwife, old wives' tale, etc. Middle English sense of "mistress of a household" survives in housewife; and later restricted sense of "tradeswoman of humble rank" in fishwife. Wife-swapping is attested from 1954.
The ordinance of marriage was sanctioned in Paradise (Gen. 2:24; Matt. 19:4-6). Monogamy was the original law under which man lived, but polygamy early commenced (Gen. 4:19), and continued to prevail all down through Jewish history. The law of Moses regulated but did not prohibit polygamy. A man might have a plurality of wives, but a wife could have only one husband. A wife's legal rights (Ex. 21:10) and her duties (Prov. 31:10-31; 1 Tim. 5:14) are specified. She could be divorced in special cases (Deut. 22:13-21), but could not divorce her husband. Divorce was restricted by our Lord to the single case of adultery (Matt. 19:3-9). The duties of husbands and wives in their relations to each other are distinctly set forth in the New Testament (1 Cor. 7:2-5; Eph. 5:22-33; Col. 3:18, 19; 1 Pet. 3:1-7).