Isai is a derivative (Hebrew) of the English and Hebrew name Isaiah.
Isai is also a derivative (English) of the English and German name Jesse.
Isai is uncommon as a baby boy name. At the modest height of its usage in 2007, 0.015% of baby boys were named Isai. It was #697 in rank then. The baby name has fallen out of favor since then, and is currently of sporadic use. Within the family of boy names directly related to Isai, Isaiah was the most frequently used in 2018.
† Pronunciation for Isai: IY as in "eat (IY.T)" ; S as in "see (S.IY)" ; AY as in "side (S.AY.D)"