Mitra

The names, and some characteristics, of these established deities subsequently influenced other figures:

• Maitreya, a vrddhi-derived form of Sanskrit mitra, a bodhisattva in Buddhist tradition.
• Latin Mithras, the principal figure of the first-century Roman mystery cult of Mithraism, whose name derives from the Avestan theonym via Greek and some Anatolian intermediate.
• In Hellenistic-era Asia Minor, Avestan Mithra was conflated with various local and Greek figures leading to several different variants of Apollo-Helios-Mithras-Hermes-Stilbon.
• In Middle Iranian, the Avestan theonym evolved (among other Middle Iranian forms) into Sogdian Miši, Middle Persian and Parthian Mihr, and Bactrian Miuro (/mihru/). Aside from Avestan Mithra, these derivative names were also used for Greco-Bactrian Mithro, Miiro, Mioro, and Miuro.
• Mithra, the "first messenger" of Iranian Manichaeans.

Indian religious texts

Both Vedic Mitra and Avestan Mithra derive from an Indo-Iranian common noun *mitra-, generally reconstructed to have meant "covenant, treaty, agreement, promise." This meaning is preserved in Avestan miθra "covenant". In Sanskrit and modern Indo-Aryan languages, mitra means "friend", one of the aspects of bonding and alliance.

The Indo-Iranian reconstruction is attributed to Christian Bartholomae, and was subsequently refined by A. Meillet (1907), who suggested derivation from the Proto-Indo-European root *mey- "to exchange".

A suggested alternative derivation was *meh "to measure" (Gray 1929). Pokorny (IEW 1959) refined Meillet's *mei as "to bind". Combining the root *mei with the "tool suffix" -tra- "that which [causes] ..." (also found in man-tra-, "that which causes to think"), then literally means "that which binds", and thus "covenant, treaty, agreement, promise, oath" etc. Pokorny's interpretation also supports "to fasten, strengthen", which may be found in Latin moenia "city wall, fortification", and in an antonymic form, Old English (ge)maere "border, boundary-post".

Meillet and Pokorny's "contract" did however have its detractors. Lentz (1964, 1970) refused to accept abstract "contract" for so exalted a divinity and preferred the more religious "piety". Because present-day Sanskrit mitra means "friend", and New Persian mihr means "love" or "friendship", Gonda (1972, 1973) insisted on a Vedic meaning of "friend, friendship", not "contract".

Meillet's analysis also "rectified earlier interpretations" that suggested that the Indo-Iranian common noun *mitra- had anything to do with the light or the sun. When H. Lommel suggested that such an association was implied in the Younger Avesta (since the 6th century BCE), that too was conclusively dismissed. Today, it is certain that "(al)though Miθra is closely associated with the sun in the Avesta, he is not the sun" and "Vedic Mitra is not either."

Old Persian Miθra or Miθ^ra – both only attested in a handful of 4th-century BCE inscriptions of Artaxerxes II and III – "is generally admitted [to be] a borrowing from the Avesta," the genuine Old Persian form being reconstructed as *Miça. (Kent initially suggested Sanskrit but later changed his mind). Middle Iranian myhr (Parthian, also in living Armenian usage) and mihr (Middle Persian), derive from Avestan Mithra.

Greek/Latin "Mithras," the focal deity of the Greco-Roman cult of Mithraism is the nominative form of vocative Mithra. In contrast to the original Avestan meaning of "contract" or "covenant" (and still evident in post-Sassanid Middle Persian texts), the Greco-Roman Mithraists probably thought the name meant "mediator". In Plutarch's 1st-century discussion of dualistic theologies, Isis and Osiris (46.7) the Greek historiographer provides the following explanation of the name in his summary of the Zoroastrian religion: Mithra is a meson ("in the middle") between "the good Horomazdes and the evil Aremanius [...] and this is why the Pérsai call the Mediator Mithra". Zaehner attributes this false etymology to a role that Mithra (and the sun) played in the now extinct branch of Zoroastrianism known as Zurvanism.