Green’s Dictionary of Slang

(US) to let go, to leave; thus hand over.

1896		H. Blossom Checkers 185: Just ‘jar loose,’ and ‘pull your freight.’.
1903		A. Adams Log of a Cowboy 243: Nor did he jar loose until we reached the water.
1908		W.G. Davenport Butte and Montana beneath the X-Ray 56: Say, Andy, you’ve just got to jar loose with five bucks for my pie card is so full of holes it looks like a piece of mosquito bar [DA].
1914		Ade ‘The New Fable of the Father Who Jumped In’ in Ade’s Fables 84: Daughter alone could induce him to un buckle, and melt, and jar loose, and come across, and kick in, and sting the Check-Book.
1930		R.E. Howard ‘Winner Take All’ Fight Stories 🌐 If you’re sports enough to jar loose and make up a purse of twenty-five dollars, I’ll fight any man in the house.
1969		‘Iceberg Slim’ Pimp 80: Jar loose from respectable scratch, bitch.
1980		Jackson & Christian Death Row 200: I was crazy, I was an insane man. Boy, it was old Satan. I was jarring him loose is what it was.