Green’s Dictionary of Slang

1. (US campus) silly, foolish, ineffectual.

1989

P. Munro Sl. U.

2. (Aus.) nervous.

1996

J. Byrell Lairs, Urgers & Coat-Tuggers 285: To spend a day with the Hendersons - if you’re like me - would usually end up in your becoming gradually and gently twitty. Twitty is the English vernacular for nervous or clownish.