Green’s Dictionary of Slang

a literal bed-wetter; or as a general derisive epithet.

[1656		Mennis & Smith et al. ‘The Answer’ Wit and Drollery 89: I Pray thee Drunkard get thee gone, / Thy Mistresse Sack doth smell too strong; / Think you I intend to wed / A sloven to be-piss my bed?].
1744		‘Nurse Lovechild’ Tommy Thumb’s Songbook II 34: Piss a Bed, / Piss a Bed, / Barley Butt, / Your Bum is so heavy / You cant get up.
1922		Joyce Ulysses 382: Pope Peter’s but a pissabed / A man’s a man for a’ that.
1933		(con. 1900s) C. McKay Banana Bottom 146: He ’fraid a you, you facey dutty nigger? Ah know you when you was de biggest piss-a-bed in Banana Bottom.
1953		S. Bellow Augie March (1996) 13: That piss-in-bed Accoucherka’s son.
1979		J. Morrow Confessions of Proinsias O’Toole 158: Concepta hissed: ‘Oul’ pee-the-bed’.