'ballplayer' originates from Modern English as a compound of 'ball' + 'player'. The element 'ball' ultimately comes from Old English/Old Norse (Old English beall / Old Norse bǫllr) meaning 'a round object used in games', and 'player' derives from the verb 'play' (Old English plega / plegian) with the agentive suffix '-er'.

'ball' appeared in Old English and Old Norse forms (e.g. Old Norse 'bǫllr') and developed into Middle English 'bal'/'ball'; 'play' (Old English 'plegian'/'plega') became Middle English 'pleien' and produced the agent noun 'player' in Middle to Early Modern English. The compound 'ballplayer' was formed in Modern English to denote someone who plays ball games, especially baseball.

Originally the elements meant simply 'a round object' (ball) and 'one who plays' (player); over time the compound narrowed to refer specifically to a person who plays ball games and, in common American usage, to a baseball player.