Latin word mirus comes from Proto-Indo-European *smey-

Detailed word origin of mirus

Dictionary entry	Language	Definition
*smey-	Proto-Indo-European (ine-pro)
*sméyros	Proto-Indo-European (ine-pro)
*smeiros	Proto-Italic (itc-pro)
mirus	Latin (lat)	Wonderful, marvelous, amazing, surprising, awesome.