mentor

English mentor comes from French mentor, from Ancient Greek Μέντωρ (Méntōr), a character in the Odyssey. His name shares a root with English mind.

The word moved from being a single mythological figure's proper name into a common noun for any trusted advisor, passing through French on its way into English.

It's cognate with Sanskrit mantṛ ("advisor, counselor") and Latin monitor ("one who admonishes"), both possibly tracing back to a Proto-Indo-European root meaning "to think" or "to warn."