Green’s Dictionary of Slang

1. an invalid.

1941		F. Sargeson ‘That Summer’ in Coll. Stories (1965) 3223: No rough house, he said. No, I said, because we don’t want any more cot cases.
1957		D. Niland Call Me When the Cross Turns Over (1958) 164: I won’t eat for days after you’ve gone. I won’t sleep. I’ll be a real cot-case.
1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 39: If I don’t get a bit of shut-eye soon I’ll be a flamin’ cot-case.
1981		(con. WWI) A.B. Facey Fortunate Life 277: Most of us were cot-cases and were in beds that were bolted to the deck of the ship.
1986		C. Bowles G’DAY 63: Players frequently go the bash, and so sometimes one of them ends up a cot case.

2. an eccentric [fig. use of sense 1].

1968

G. Slatter Pagan Game (1969) 162: His one desire was to sing soprano in the village choir — A real cot case.

3. a drunkard; one suffering from a hangover or DTs.

1959		G. Slatter Gun in My Hand 199: All I can see is hopheads on the bash and they’ll all be cot cases tomorrow and sorry as hell.
1988		McGill Dict. of Kiwi Sl. 30/1: cot case lunatic or very drunk, fit only for a cot or baby’s enclosed bed.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].