The story
Derives from the obsolete Elizabethan-era slang use of the word jig, originally meaning a lively dance, which evolved to denote a practical joke or trick.
Etymology from Wiktionary, CC BY-SA 4.0.
the jig is up
Today it means: Used to express that a deception, trick, or dishonest scheme has been discovered, signaling the end of the ruse. Full definition →