Green’s Dictionary of Slang

1. (also croc) a horse, esp. a broken-down, old horse.

1838		R.S. Surtees Jorrocks Jaunts (1874) 97: ‘Short-odds Richards’ on a long-backed crocodile-looking rosinante.
1853		R.S. Surtees Mr Sponge’s Sporting Tour 10: He [...] quilted the old crocodile of a horse all the way home.
1856		‘The Druid’ Post and Paddock 242: Mr. Waterton used to say that it was his practice with the Badsworth, which gave him ‘such a fine hand on a crocodile’.
1897		Worker (Brisbane) 4 Sept. 8/3: [He] knocks about the whole year long around his drought-struck isle, / Across a wiry ‘cuddy’ whom he calls his ‘crocodile’.
1897		Worker (Brisbane) 4 Sept. 8/4: Now when the shed at last ‘cuts out’ he gets his ‘little bit,’ / And straps his ‘peter’ on his ‘croc’ and quickly does a get.
1906		Sydney Morn. Herald 11 July 6/1: The everyday and all-day kind of quadruped is most often referred to as a ‘prad’, but he is almosr certain to come also under such descriptions as ‘insect,’ ‘crocodile’ (condensed to ‘crock’) and ‘cuddy’.
1938		D. Runyon ‘It Comes Up Mud’ Runyon on Broadway (1954) 531: One or two crocodiles that he calls race horses.
1945		Baker Aus. Lang. 71: The old Scottish use of crock for a broken-down horse has probably influenced the evolution of the Australian out-back slang crocodile and alligator for a horse.

2. (Aus.) a roustabout [fig. use of sense 1].

1900

Bulletin (Sydney) 18 Aug. 14/3: A good bushman rarely repeats himself either in swearing or slanging; for instance, the shearer terms the rouseabout variously a ‘loppy,’ ‘bluetongue,’ ‘wop-wop,’ ‘leather-neck,’ ‘crocodile,’ &c.