Nun

Nun (0. Eng. nunne, from Lat. nonnus, nonna, familiar terms for an old man or woman), a member of a community of women, living under vows a life of religious observance (see Monasticism). In ecclesiastical Latin nonnus was used by the younger members of a religious community for their elders, and so, in the regula  of St Benedict, cap. 62, Juniores autem Priores suos nonnos vocant quod intelligitur paterna reverentia (Du Cange, Glossarium, s.v. nonnus). While nonna has remained as the generic name of a female religious, nonnus has been replaced by monachus  and its various derivatives (see Monk).