Isai is a ♂ male name.
The name Isai is an e.g. German cognate of the biblical name Jesse, which is of Hebrew origin (Old Testament: Jesse is the father of King David).
Isai means “gift of God” (from Hebrew “sháy/שַׁי” = present/gift), but as well “God exists” (from Hebrew “yésh/יֵשׁ” = there is/there exist).