Etymology

From Proto-Indo-Iranian *mitra ‎(literally “(that which) causes binding”), from Proto-Indo-European *mey- ‎(literally “to bind”).

Cognate with Sanskrit मित्र ‎(mitrá) [cf. Mitra].
Avestan proper noun was also borrowed into Old Persian 𐎷𐎰𐎼 ‎(Miθra), and (nominally only) via Greek into Latin Mithras.