Green’s Dictionary of Slang

a depressing, censorious person.

1953		J. Franklyn Cockney 275: ‘Worrygut’, ‘Miserygut’, ‘Grizzlegut’ all speak for themselves.
1968		S. Gore Holy Smoke 47: When old misery guts takes a gink at Shad, Mesh and Ab.
1972		Galton & Simpson ‘Loathe Story’ Steptoe and Son [TV script] He doesn’t seem anything like a misery-guts.
1981		G. Johnston Fish Factory 108: Don’ be such a spoil-sport and misery guts.
1995		J. Stahl Permanent Midnight 127: Ask her what she thought of her son, she’d sneer, ‘Misery guts.’.
2003		McGill Reed Dict. of N.Z. Sl.
2004		E. Murfin Sabbatical 86: He was regarded [as] standoffish or withdrawn or even as a miseryguts. He had long been made to realise that the miseryguts is not highly regarded.