Green’s Dictionary of Slang

kangaroo n.1

1. [mid-19C+] (US) an Australian; an Australian soldier; an Aborigine.

2. [late 19C–1900s] a thin, slope-shouldered person [the supposed resemblance to the animal].

In compounds

kangaroo feathers (n.) [kangaroos do not have feathers; the susceptibility of hearers to the story (retailed in the Boer War by the Australian Bushrangers and in WW1 by Anzac infantry the Prince of Wales Light Horse) that the feathers in their bush hats were ‘kangaroo feathers’; ]

[1910s] (Aus.) an impossible thing, often an unlikely story, often combined with ‘molasses mines’ or ‘goanna farms’ as the epitome of absurd impossibility.

kangaroo hop (n.)

[late 19C] (Aus.) a short-lived feminine affectation in which the hands were held palm-down at the breast, a pose reminiscent of the kangaroo.

Kangarooland (n.)

[mid-19C+] (Aus.) Australia, thus Kangaroolander, Australian.

kangaroo shit (n.)

[1940s+] (Aus.) defecation in a squatting position.

kangaroo straight (n.) [suggested by the gaps or ‘jumps’]

[1950s+] (US) a poker hand which resembles a straight but has a card or cards missing, thus a worthless hand.

Kangaroo Valley (n.)

1. [1960s+] Earls Court, London, base for many expatriate Australians.

2. attrib. use of sense 1.

In phrases

have kangaroos in one’s/the (top) paddock (v.) (also have possums...) [SE top paddock, used fig. for the head]

[20C+] (Aus./N.Z.) to be eccentric, to be mentally unstable.

a kangaroo short in the top paddock (also short of a few kangaroos in the top paddock)

[1990s+] (Aus.) a phr. describing a fool.