gamer (n.) Look up gamer at Dictionary.com
mid-15c., "an athlete" (mid-13c. as a surname, Johannes le Gamer), agent noun from game (v.). Meaning "one devoted to playing video or computer games" is attested by 1981 (by 1975 in reference to players of Dungeons & Dragons). Gamester is attested from 1590s but meant "prostitute" (compare old slang the first game ever played "copulation"), later "a man fit and ready for anything, a player" (mid-17c.).
Quite a few of the gamers we've encountered during our monthly strolls down "Arcade Alley" suffer the same chronic frustration: finding enough opponents to slake their thirst for endless hours of play. ["Video" magazine, May 1981]