What does "butterflies in your stomach" mean — and why is it funny?

informal

Meaning

A fluttering, nervous feeling, usually before something exciting or frightening.

Where it comes from

A twentieth-century phrase. The light, flickering sensation of nerves is likened to the movement of butterfly wings.

Why it is funny

The humor is the prettiness of the picture for something so uncomfortable. Anxiety gets recast as a swarm of delicate butterflies fluttering around inside you, turning a churning stomach into something almost charming.

Used in a sentence

"I had butterflies in my stomach before walking on stage."