early 15c., "pleasant pastime," shortening of disport "activity that offers amusement or relaxation; entertainment, fun" (c. 1300), also "a pastime or game; flirtation; pleasure taken in such activity" (late 14c.), from Anglo-French disport, Old French desport, deport "pleasure, enjoyment, delight; solace, consolation; favor, privilege," related to desporter, deporter "to divert, amuse, please, play" (see sport (v.)), also compare disport (n.).
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. The sport of kings was originally (1660s) war-making. Other, lost senses of Middle English disport were "consolation, solace; a source of comfort."
word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).