Green’s Dictionary of Slang

(orig. N.Z. milit.) boots, orig. those issued to ‘other ranks’.

1922		Truth (Wellington) 3 June 5/6: He heard a noise on Fowld’s roof, which made him think that the sparrows were sleep-walking with Bill Massey’s on.
1941		Ellesmere Guardian (N.Z.) 7 Apr. 4/3: ‘Bill Massey’s’ were not exactly the kind of footwear to tread on polished lino.
1942		Eve. Post (Wellington) 9 June 4/5: The woollen socks don’t stand up to many hours’ hard wear [...] in today’s version of good old Bill Massey’s.