Dictionary of Medieval Names
from European Sources

Transmundus m. Latin trans 'across, over, beyond; on the other side' + Latin mundus 'world'.

This phrase, more often used as a byname, was also rarely used as a given name.

Italy
Latin
1285 Transmundi (gen) Perugia1285 p. 154
Cite as: S.L. Uckelman. "Transmundus". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2017, no. 1. http://dmnes.org/2017/1/name/Transmundus.