“Mettre les pouces” is a French idiom that literally means “to put the thumbs.” What it really means is to stop resisting, to give in, to admit defeat or to abandon something.

It dates from the end of the 18th century. In that same era, a similar expression “coucher les pouces” (to put the thumbs to bed, or to rest the thumbs) also existed.

The exact origin of this phrase is unknown, but there are three theories. One is that it comes from ancient Rome, when the spectators of a gladiatorial event would raise or lower their thumbs to indicate whether they wanted a victorious gladiator to spare or take the life of the vanquished fighter.

Another theory is that when someone puts down a weapon, only then can the fighter’s thumb come to rest.

The third theory is that this saying comes from the use of thumb cuffs (poucettes), used to imprison the thumbs of a prisoner (rather than his wrists, which is what handcuffs do). Once the prisoner had been made to “mettres les pouces,” he was incapable of any further resistance to his jailers.

Equivalent English sayings include “to throw in the towel” or “to give in.”