champion (n.)
early 13c., "doughty fighting man, valorous combatant," also (c.1300) "one who fights on behalf of another or others," from Old French champion "combatant, champion in single combat" (12c.), from Late Latin campionem (nominative campio) "gladiator, fighter, combatant in the field," from Latin campus "field (of combat);" see campus. Had been borrowed earlier by Old English as cempa. Sports sense in reference to "first-place performer in some field" is recorded from 1730.
champion (v.)
"to fight for, defend, protect," 1820 (Scott) in a literal sense, from champion (n.). Figurative use by 1830. Earlier it meant "to challenge" (c.1600). Related: Championed; championing.