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Dictionary of Medieval Names
from European Sources

Hartois f. Old Saxon hard, Old High German hart 'strong, hard' + Old Saxon widu, wido, Old High German witu 'wood'.

France
Latin
c823 Ardois (nom) irminon-vol2 15, Wan
Cite as: S.L. Uckelman. "Hartois". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2018, no. 1. http://dmnes.org/2018/1/name/Hartois.