Dictionary of Medieval Names
from European Sources

Iarncum m. Old Breton (ho)iarn 'iron' + Old Breton cum 'gentle, beloved'.

France
Latin
833 Iarncum (nom) CartRed V
Cite as: S.L. Uckelman. "Iarncum". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2016, no. 4. http://dmnes.org/2016/4/name/Iarncum.