Where does “Yernagh” come from?

Yernagh (Manx) comes from Old Irish Érennach, from Old Irish Ériu, from Primitive Irish *Īweriū, from Proto-Celtic Φīweryū, from Proto-Indo-European piHweryon-, from Proto-Indo-European peyH- — fat, milk.

Yernagh (Manx): Irish; Irishman, Irishwoman