What does this gesture with the thumb tucked between the fingers mean?

A protective symbol with ancient origins
Before entering common parlance, the gesture had a deeper meaning. In several Eastern European traditions, particularly in folk cultures, it was considered a small talisman against unwanted influences.

The fist symbolized inner strength, and the bent thumb represented a “key” meant to preserve positive energy. This symbol was sometimes carried in a pocket or under a coat to instill courage, just as we might carry a lucky charm today.