Apparently, in the bad old days “jig” was interchangeable with the n-word.
How do I know this? 1989’s “Harlem Nights” set in the thirties used it liberally.
I also recall “jigaboo” being spat out by one of the baddies in 1984’s “Police Academy” (Bubba Smith then proceeds to tear him a new one).
And they say Hollywood can’t teach history.
the jig is up (simple past the jig was up)
(US, idiomatic) An expression used to mean “We have been caught out and have no defence”, or if spoken to a person who’s just been found out as the perpetrator of an offense, it means “You’ve been discovered.”
1753, The Skipper
We knew then the jig was up, and it was no grin matter for us.
1833, Seba Smith (as Jack Downing), The life and writings of Major Jack Downing, of Downingville, away down East in the State of Maine, Lilly, Wait, Colman & Holden, page 176,
When I first told ‘em how the jig was up with us, that the British were going to have the land, without any fighting about it, I never see fellows so mad before in my life, unless it was Major Eaton at Washington when he sot out to flog Mr. Ingham.
1920, Champ Clark, My Quarter Century of American Politics, Harper & brothers, page 96,
After I had returned home in the spring of 1893 from Washington, where I saw so many gray-haired men who had held high elective office begging for the crumbs from Cleveland’s table, I gave my wife an account of what I observed, and told her that when the jig was up for me I would hasten back to Missouri to begin the practice of law once more and be a man among men.
2007, Mary Newport, in Jerry Newport and Mary Newport, Mozart and the Whale: An Asperger’s Love Story, Simon and Schuster, ISBN 074327282X, page 248,
The universe works in strange ways: just when you think the jig is up, you get a second chance.
[edit] Synonyms
Gotcha!
the game is up
[edit] Alternative forms
jig’s up
one’s jig is up
one’s jig’s up
the jig’s up
There’s more, but I’ve decided to be somewhat niggardly with further info.