pozzyn.

1900 Worcs. Chron. 18 Aug. 2/7 ‘A little more “pozzy” would be all right, too, Sir,’ said my friend. ‘What's pozzy?’ Methuen asked, smilingly. ‘Jam, Sir,’ chorussed the men.

1915 L. Smith Gunner's Ballad in Lancaster (Pa.) Daily Eagle 4 Jan. 3/2 ‘Pass up the pozzy, if it's not all done.’ But hark. ‘Eyes front, turn out and man your gun.’ There goes the tea, the jam is on the floor.

1919 W. H. Downing Digger Dial. 59 Pozi, jam. ‘Who puckeroed the pozi?’ ‘Who took the jam?’

1929 Papers Michigan Acad. Sci., Arts & Lett. 10 316/1 Possie, jam. This seems to be a variant of pozzi (or pozzy).

1962 W. Granville Dict. Sailors' Slang 91/1 Pozzie (y), jam or marmalade.

2001 East Bay Express (Calif.) 25 May During WWI, British army slang included a word for tinned jam—‘pozzy’—that was issued as part of the field ration; the regular plum and apple pozzy was supplemented later on by exotic mixtures of gooseberry and rhubarb.