Jelsy is of Germanic origin, derived from the ancient personal name Hельsа, which means 'defender of mankind'. The name was brought to France by the Franks and Normans during their invasions in the Middle Ages. In French, it evolved into 'Gelais' and later 'Jelsy'. This unique given name has a strong historical lineage while retaining a distinctive character.
The name Jelsy saw two peaks in popularity, with five babies named Jelsy each in 1999 and 2005.