Dictionary of Medieval Names
from European Sources

Gerosmus m. Old High German, Old Saxon gēr 'spear' + Latin -is(s)(i)mus, a superlative suffix.

France
Latin
c823 Gerosmus (nom) irminon-vol2 9, Gaugiacum
Cite as: S.L. Uckelman. "Gerosmus". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2016, no. 4. http://dmnes.org/2016/4/name/Gerosmus.