'ballgame' is a Modern English compound formed from 'ball' + 'game'; 'ball' comes (via Middle English) from Old Norse 'bǫllr' meaning 'a round object', and 'game' comes from Old English 'gamen' meaning 'joy, amusement'.

'ball' changed from Old Norse 'bǫllr' to Middle English 'ball', and 'game' changed from Old English 'gamen' to Middle English 'game'; the compound 'ball-game' appeared in Modern English (19th century) and later became written as 'ballgame'.

Originally referring to play or amusement involving a ball, the term evolved to refer specifically to an organized sporting contest using a ball (in American usage often specifically baseball).