The word hero entered English around the 14th century, but its roots reach back to the earliest layers of Greek civilization. In Homer's epics, a hḗrōs was not simply a brave person — it was a specific class of being, mortal yet touched by divinity, whose deeds would echo through eternity.
The Greek hḗrōs may trace to Proto-Indo-European *ser- meaning 'to protect', making the original hero literally a guardian or protector of the people. This military dimension is key: Greek heroes were warriors first, moral exemplars second.
What makes the etymology fascinating is the religious dimension. Greek heroes received cult worship after death. Cities competed to claim heroes' burial sites, believing their presence brought divine protection. Theseus was 'relocated' to Athens for precisely this reason.
The word passed through Latin hērōs into Old French before reaching English. The modern meaning — simply 'a person admired for bravery' — would have puzzled the Greeks, for whom heroism required a divine bloodline. Our democratisation of heroism is a purely modern invention.