Green’s Dictionary of Slang

(US) anxiety, nervousness.

1935		G. & S. Lorimer Heart Specialist 47: In as a complete a state of jits as I was [HDAS].
1942		Berrey & Van den Bark Amer. Thes. Sl.
2006		F.X. Toole Pound for Pound 277: On the morning of the fight, Chicky had the jits.