Green’s Dictionary of Slang

shitless adv.

to an extreme extent.

1950		E. Hemingway letter 11 June in Baker Sel. Letters (1981) n.d. 696: I’d done 42 galleys from 0600 to 1300 and was bored shitless. [Ibid.] 852: 5 Dec.: You are probably bored shitless by now.
1965		W. Eastlake Castle Keep (1966) 145: I’ll bore them shitless with military tactics.
1971		B. Malamud Tenants (1972) 56: On my first solo gig I was bagged out of my own stupidity, beaten shitless, and dumped in jail.
1978		Tracks (Aus.) Dec. 3: Don’t listen to all the shit that gets put on Victoria. Victorians know they have the best state, they don’t have to rave shitless [Moore 1993].
1979		D. Maitland Breaking Out 263: Sweating in the fierce heat of the quadrangle and already bored shitless by the whole affair.
1986		R. Fitzgerald Pushed from the Wings (1989) 68: Merv’s worried shitless.
1989		P. Munro Sl. U. 208: worried shitless very worried.
1998		I. Welsh Filth 71: Bored shitless here.
2003		N. Green Angel of Montague Street (2004) 215: I was bored shitless most of the time.
2006		G. Malkani Londonstani (2007) 277: Guys [...] that he’d beaten shitless over the years.
2007		L. Redhead Cherry Pie [ebook] Bored shitless by all those old farts talking politics.
2015		G. Disher Heat [ebook] Saturday afternoon, bored shitless and counting the minutes until she knocked off.

In phrases