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

We’ve all seen it somewhere: a clenched fist, with the thumb tucked under the index and middle fingers. A tiny, almost childish gesture… yet loaded with surprisingly rich symbolism. Somewhat forgotten today, this gesture has transcended eras, regions, and even families. Sometimes it meant “no,” sometimes “protect yourself,” sometimes “just kidding.” So how did a simple bent thumb tell so many stories? That’s what we’ll explore together.