Green’s Dictionary of Slang

1. cocoa.

1935		M. Harrison Spring in Tartarus 300: He understood well enough, why the cocoa which Jim sold at a penny a cup, was called ‘shell-shock’.
1943		M. Harrison Reported Safe Arrival 109: Fancy a cupper shell-shock?

2. (US) a joc. term of address; the implication is that the subject has an ‘explosive’ personality.

1920

F.S. Fitzgerald ‘Bernice Bobs Her Hair’ in Bodley Head Scott Fitzgerald V (1963) 102: She would not have treated him to the line which began ‘Hello, Shell Shock!’.

3. (UK tramp) tea served in a casual ward or hostel.

1984

Partridge DSUE (8th edn) 1048/1: from ca. 1919.

4. (Aus./N.Z.) a mixed alcoholic drink, usu. very potent, e.g. port and stout.

1941		Baker Popular Dict. Aus. Sl.
2003		McGill Reed Dict. of N.Z. Sl. 185: shellshock Alcoholic spirits. ANZ mid C20.