heroism (n.)

late 14c., "man of superhuman strength or physical courage," from Old French heroe (14c., Modern French héros), from Latin heros (plural heroes) "hero, demi-god, illustrious man," from Greek hērōs (plural hērōes) "demi-god." This is of uncertain origin; according to an old theory perhaps originally "defender, protector" and (Pokorny, Watkins) from PIE root *ser- (1) "to protect," but Beekes writes that it is "Probably a Pre-Greek word."

In Homer, of the Greeks before Troy, then a comprehensive term used of warriors generally, also of all free men in the Heroic Age. In classical mythology from at least the time of Hesiod (8c. B.C.E.) "man born from a god and a mortal," especially one who had done service to mankind; with the exception of Heracles limited to local deities and patrons of cities.

In English the meaning "man who exhibits great bravery" in any course of action is from 1660s. The sense of "chief male character in a play, story, etc." is recorded by 1690s. Hero-worship is from 1713 in reference to ancient cults and mysteries; of living men by 1830s.