The north door used to be so called. The menservants and other poor men used to sit on benches down the north aisle, and the maidservants, with other poor women, on the south side. Even when married the custom was not discontinued. After service the men formed one line and the women another, down which the clergy and gentry passed amidst salutations, and the two lines filed off. In some country churches these arrangements are still observed.
“Bachelors' wives and old maids' children be well taught.” —Heywood: Proverbs.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894