Green’s Dictionary of Slang

(US) a joc. imitation of a Southern pron. of shit! excl.

1951		Kerouac On the Road (The Orig. Scroll) (2007) 352: Sheeit, and you’ve got to look out for your boy.
1968		N. Heard Howard Street 151: ‘Shee-it!,’ Jackie hooted. ‘Man, you really don’t know where it’s at, do you?’.
1976		N. Thornburg Cutter and Bone (2001) 245: Why shee-it, man, I be able to re-tire on Ibiza.
1985		J. Morrison Share House Blues 59: ‘Shee! Not even a forty hour week’.
1986		R. Campbell In La-La Land We Trust (1999) 57: Shee-it [...] You want coffee?
1994		N. McCall Makes Me Wanna Holler (1995) 254: My five-year plan? Sheeeiiit!
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 164: He mimed a gutting stroke. He said, ‘Sheeit. Like a dressed hog, man.’.
2012		C. Rosmus ‘Hangdog’ in C. Rhatigan and N. Bird (eds) Pulp Ink 2 [ebook] ‘I don’t want it [...] I’d drink my own piss first.’ ‘Sheee-itt,’ Speed said.