Dictionary of Medieval Names
from European Sources

Precious f. Middle English precious, Old French precios from Latin pretiōsus 'precious, dear, costly'.

England
Latin
1379 Preciosa (nom) WRYPT1 p. 5
Cite as: S.L. Uckelman. "Precious". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2017, no. 1. http://dmnes.org/2017/1/name/Precious.