Mitra is the name of an Indo-Iranian divinity that predates the Rigvedic Mitrá and Avestan Mithra.
Mithra (left) in a 4th-century investiture sculpture at Taq-e Bostan in western Iran.
Mithras-Helios, in Phrygian cap with solar rays, with 1st century BC Antiochus I Theos of Commagene. Found at Mount Nemrut, in present-day eastern Turkey.
Relief of Roman Mithras, in a tauroctony scene.
The Indo-Iranian peoples, also known as Ā́rya or Aryans from their self-designation, were a group of Indo-European speaking peoples who brought the Indo-Iranian languages to major parts of Eurasia in waves from the first part of the 2nd millennium BC onwards. They eventually branched out into the Iranian peoples and Indo-Aryan peoples.
Rigveda manuscript page (1.1.1–9)
Yasna 28.1 (Bodleian MS J2)