ball boy

WordReference Random House Unabridged Dictionary of American English © 2025

ball′ boy′, 

1. Sport [Tennis.] an attendant, usually a boy or young man, employed to retrieve balls and supply players with them.
2. Sport [Baseball.] an attendant, usually a boy or young man, who retrieves foul balls and brings the umpire new balls during the game.
• 1900–05

Collins Concise English Dictionary © HarperCollins Publishers::

ball boy, ball girl noun

1. (in sport, esp tennis) a person who retrieves balls that go out of play