The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
box office
NOUN:
1. A booth, as in a theater or stadium, where tickets are sold. 2a. The drawing power of a theatrical entertainment or of a performer; popular appeal. b. A factor influencing this power: Notoriety is usually good box office.3. Total attendance for an entertainment; turnout. 4. The amount of money received from ticket sales for an entertainment.
ETYMOLOGY:
So named because it was originally an office for the booking of boxes in a theater.