Green’s Dictionary of Slang

nervous, tense, ‘on edge’.

1931		K.C. Times 13 Nov. 22: The editors will go home all jittery unless the Junior League girls [...] quit parading around the mezzanine [DA].
1939		P. Cheyney Don’t Get Me Wrong (1956) 49: When she pulled that fake gun act on me I got jittery.
1947		B. Schulberg Harder They Fall (1971) 218: The morning of the fight [...] all of us were jittery.
1951		M. Spillane One Lonely Night 69: Henry Gladow was a jittery little man.
1961		R. Gover One Hundred Dollar Misunderstanding 19: She-it! This one walk like he ain got no toes. Jittery? Kee-ryess is he jittery.
1975		‘P.B. Yuill’ Hazell and the Three-card Trick (1977) 133: I hear he’s stuck in a bedroom in Brixton too jittery ever to face the street again.
1982		G.V. Higgins Patriot Game (1985) 20: They been getting very nervous about the thing all over the damned country and as soon as they get jittery they send for me.
1999		Observer Business 25 July 6: The reaction to Smith-Kline’s interims [...] showed how jittery the market is.