'underbooking' originates from the prefix 'under-' meaning 'below' and the word 'booking' from 'book,' which meant 'to reserve.'

'underbooking' evolved from the practice of 'booking' fewer reservations than capacity, a term that became more common in the travel and hospitality industries.

Initially, it meant 'booking below capacity,' and this meaning has largely remained the same in modern usage.