Green’s Dictionary of Slang

1. (orig. US campus) eccentric, odd, insane.

1928		St Louis Post-Disptach (MO) 25 June 21/4: Harassed papa, petite mamma, squirrely son and cute daughter.
1931		Harrisburgh Teleg. (PA) 28 Oct. 13/6: ‘Squirrely’ seems to be the favored adjective. So-and-so’s ‘squirrely’.
1938		A.J. Liebling Back Where I Came From (1990) 205: The women waking fretfully to claw their partners’ faces and scream. This was known as ‘going squirrelly.’.
1942		N. Algren Never Come Morning (1988) 44: He’s gettin’ so squirrelly he loses count.
1959		E. De Roo Go, Man, Go! 7: Pa saw squirrely Gill in the Merc.
1961		J. Kirkwood There Must Be a Pony! 234: It sounds squirrely and I guess it was.
1977		L. Heinemann Close Quarters (1987) 156: The kid watched those sheep every damn night, pulling his pud and whatnot, get a little more squirrelly each night.
1981		(con. 1930s) O’Day & Eells High Times Hard Times 37: Kids often got squirrelly during those quiet moments.
1991		P. Cornwell Body of Evidence (1992) 377: He saw it coming – what his squirrelly pal finally did to Beryl.
2001		J. Stahl Plainclothes Naked (2002) 218: Tina and Manny ran into [the pretzel vendor] after leaving the squirrelly plastic surgeon, and Manny insisted on stopping.
2018		(con. 1963) L. Berney November Road 120: Miami. Klaus, the sneakiest, squirrelliest, most reliably untrustworthy ex-Catholic ex-Commie ex-Nazi in the Western Hemisphere.

2. (US) reckless; also as adv., recklessly.

1966		Current Sl. I:1 4/1: Squirrely To be belligerent, excitable.
1968		‘Sl. of Watts’ in Current Sl. III:2 45: Squirrelly, adv. In a high-spirited way; recklessly.
2008		T. Piccirilli Fever Kill 77: That was an affront. It was squirrelly, not giving an answer.

3. nervous.

1987		T. Wolfe Bonfire of the Vanities 365: The guy gets squirrelly when two cops come to his apartment to question him.
1993		T. Jones Pugilist at Rest 172: She was squirrelly as hell and she couldn’t lie down.
2002		T. Dorsey Triggerfish Twist (2002) 270: ‘He got buggy and spooked.’ ‘Then he went squirrelly.’.
2009		J. Stahl Pain Killers 275: Carlos was getting squirrelly. I tried to keep it casual.
2021		T. Swerdlow Straight Dope [ebook] — Can I crash with you tonight, I’m feeling really squirrely,.