This idiom comes from an old story by Liu Zongyuan.
Long ago in Guizhou, there were no donkeys.
One day, someone brought one in by boat and left it at the foot of a mountain.
A tiger saw the strange animal and didn’t dare go near.
So it hid in the woods, watching quietly.
Over time, the tiger grew bolder and crept closer.
One day, the donkey let out a loud bray.
The tiger jumped — was this creature dangerous?
But… nothing happened.
Days passed.
The tiger got used to the sound.
It even bumped into the donkey. Still, no danger.
Finally, the donkey got angry and kicked.
That was it.
The tiger laughed, realizing that was its only trick.
So it pounced, killed the donkey, and ate it.
That became a metaphor:
When someone has only a few weak skills — and they’ve already used them — they’re out of tricks and exposed.