“I cross my fingers for you!” – A phrase to wish someone good luck or success in an upcoming exam or the like. But how exactly are crossed fingers supposed to help you achieve your best performance and where does the well-known expression come from?

The fact is: the thumb is a special and even the most important finger on the human hand. It is particularly flexible and at the same time the strongest finger. Thanks to the thumb, man can reach out and hold onto things. But why are fingers crossed in a non-verbal gesture to wish someone luck? First of all, opinions are divided on the question of whether both fingers have to be crossed or just one. The answer is: both. After all, the idiom is “fingers crossed” rather than “fingers crossed.” In addition, there is a lack of clarity about how to cross your fingers correctly. Thumbs up or in a closed fist? Correct is: in the closed fist. This is the only way to wish someone luck. Why this is so is explained by looking at the origin of the phrase.

Strictly speaking, there are two assumptions as to where the saying comes from: A tradition says that the Germanic peoples coined the expression. The people already believe that if you keep your fingers crossed for someone, it influences fate in a positive way. For them, the fat finger was a symbol of goblins and demons. So if you crossed your fingers, you symbolically grabbed the evil spirits and held them tight. In this way you could prevent the goblin – in the shape of the thumb – from doing practical jokes. A modified form of this origin story says that the thumb was a kind of lucky finger with magical powers among the Germans. And you just had to hold on to happiness.

The other origin story suggests that the proverb had its origins in ancient Rome. Crossing fingers was already known there, too: This is documented by a quote from the Roman naturalist Pliny the Elder. 2000 years ago he collected the natural history knowledge of his time and compiled it in an encyclopedia. It contains the following Latin sentence: “Pollices, cum faveamus, premere etiam proverbio iubemur.” Translated this means: “Even the proverb tells us to keep our fingers crossed if we are inclined to someone”. This sentence suggests that the phrase “fingers crossed” already existed back then.

In fact, there are sources that describe how fingers crossed played a major role in gladiator fights. After each fight, the audience decided whether the loser got to live or die. When viewers wanted to express their sympathy for the defeated gladiator and ensure that he was pardoned, they raised their hands and locked their thumbs between the remaining fingers. The thick finger symbolized the deadly sword for the Romans. So with the gesture they made it clear that the sword should be put back in the holder. If the Romans stuck out their thumbs, it meant: sword out, head off.

This is often misrepresented in movies. There, the spectators hold the raised thumbs up to express that the gladiator should stay alive. Thumbs down again means he should die. The film industry probably makes use of these hand movements because today’s viewers would not understand the historical thumb-crossing gesture in this context. Thumbs up or down, however, is more understandable.