What is the origin of the idiom "thumbs up" and when to use it?

The idiom "thumbs up" has its origin in ancient Roman culture, where a thumbs up gesture was used as a sign of approval or agreement. Gladiatorial contests in ancient Rome often involved life-or-death situations, and the crowd would signal their preference for the fate of the defeated combatant. A thumbs up indicated that the crowd wished the gladiator to be spared, while a thumbs down meant a fatal blow. Over time, the thumbs up gesture evolved into a universally recognized sign of positive affirmation or approval.