nun: [OE] In medieval Latin, nunnus and nunna were titles of respect accorded respectively to old men and old women in general. In due course they came to be applied specifically to ‘monks’ and ‘nuns’. The masculine form has since disappeared, but the feminine nonna was borrowed into Old English as nunne. This was subsequently reinforced in the 13th century by Old French nonne. [nun etymology, nun origin, 英语词源]