mentor

Every mentor today is named after a man who was already named after the thing he did. Greek Méntōr is built from menos (spirit, intent, force-of-thought) plus -tōr, the Greek agent suffix that does the same work as Latin -tor — it makes "one who Vs" nouns. So the name reads, in plain Greek, "one who minds" or "one who thinks-for-you." But in Homer it doesn't function as a label. It functions as a name. Mentor in the Odyssey is a particular man, a friend of Odysseus, entrusted with Telemachus when his father leaves for Troy. The wisdom-giving in the poem is doubled: Athena keeps taking Mentor's form to guide the boy, so much of the advice in the story is divine wearing a human face. The Greeks heard the etymology — the suffix was alive — but the word stayed a proper noun for the better part of three thousand years.

The shift happens through a single book. In 1699, François Fénelon publishes Les Aventures de Télémaque, written for his pupil the Duke of Burgundy: a moralizing sequel to the Odyssey in which the character Mentor delivers chapter-long pedagogical speeches to Telemachus on every aspect of how to rule and how to live. The book is enormously popular through the 18th century — translated everywhere, read in courts, given to young princes and young men of letters. By the time Mentor appears in dozens of imitations and references, the proper noun has begun to slip. A Mentor, in 18th-century French and then English, comes to mean "a wise instructor in the style of Fénelon's Mentor." Capitalized, then lowercased. The literary character has become a type, the type has become a role, the role has become a common noun. Chesterfield uses mentor in his Letters by 1750.

The verb is much later — mid-20th-century American English, from corporate and educational contexts: to mentor, "to advise and develop a junior." By then the link to Homer is paper-thin. Most people who use the word have no memory of the character. The common noun has run free of its origin so completely that the origin sounds, when you find it, almost like a coincidence — wait, there was an actual Mentor? Yes, and his name already meant what we now use his name to mean. The arc is unusual but not unique: maverick (from Samuel Maverick, a Texas rancher), boycott (from Captain Boycott), sandwich (from the Earl of Sandwich). Mentor differs in being a name that was always already descriptive of the person. Mentor was already, in Greek, "one who minds." The eponym is just the cycle closing.