in the modern sense of a game of ball for teams of nine, 1845, American English, from base (n.) + ball (n.1). Earlier references, such as in Jane Austen's "Northanger Abbey," refer to the game of rounders, of which baseball is a more elaborate variety. The modern game was legendarily invented 1839 by Abner Doubleday in Cooperstown, N.Y. Base was used for "start or finish line of a race" from 1690s; and the sense of "safe spot" found in modern children's game of tag can be traced to 15c. (the use in reference to the bags in modern baseball is from 1868). Baseball as "ball with which the game of baseball is played" is by 1885.
c. 1200, from Old English gamen "joy, fun; game, amusement," common Germanic (cognates: Old Frisian game "joy, glee," Old Norse gaman "game, sport; pleasure, amusement," Old Saxon gaman, Old High German gaman "sport, merriment," Danish gamen, Swedish gamman "merriment"), said to be identical with Gothic gaman "participation, communion," from Proto-Germanic *ga- collective prefix + *mann "person," giving a sense of "people together."
The -en was lost perhaps through being mistaken for a suffix. Meaning "contest for success or superiority played according to rules" is first attested c. 1200 (of athletic contests, chess, backgammon). Especially "the sport of hunting, fishing, hawking, or fowling" (c. 1300), thus "wild animals caught for sport" (c. 1300), which is the game in fair game (see under fair (adj.)), also gamey. Meaning "number of points required to win a game" is from 1830. Game plan is 1941, from U.S. football; game show first attested 1961.