In the film "The Great Gatsby," Mr. Gatsby says "Sorry, old sport, I thought you knew"; what is the meaning of old sport?
Original sense preserved in phrases such as in sport "in jest" (mid-15c.). Meaning "game involving physical exercise" first recorded 1520s. Sense of "stylish man" is from 1861, American English, probably because they lived by gambling and betting on races. Meaning "good fellow" is attested from 1881 (as in be a sport, 1913). Sport as a familiar form of address to a man is from 1935, Australian English.