1845, Amer.Eng., from
base (n.) +
ball. Earlier references, e.g. in Jane Austen's "Northanger Abbey," refer to the game of "rounders," of which baseball is a more elaborate variety. Legendarily invented 1839 by Abner Doubleday in Cooperstown, N.Y.
Base was used for "start or finish line of a race" from 1695; and the sense of "safe spot" found in modern children's game of tag can be traced to 14c. The sense in baseball is from 1868. Fig. sense
get to first base "make a start" (1938) is from baseball.
[beys-bawl] 
