protagonist (n.)

1670s, "principal character in a story, drama, etc.," from Greek prōtagōnistēs "actor who plays the chief or first part," from prōtos "first" (from PIE root *per- (1) "forward," hence "in front of, first, chief") + agōnistēs "actor, competitor," from agōn "contest" (from PIE root *ag- "to drive, draw out or forth, move"). Meaning "leading person in any cause or contest" is from 1889. Mistaken sense of "advocate, supporter" (1935) is from misreading of Greek prōtos as Latin pro- "for." Compare antagonist. Deuteragonist "second person or actor in a drama" is from 1840.