"of or pertaining to the implacental mammals," who usually are provided with a pouch for their young, 1690s, with -al (1) + Modern Latin marsupialis "having a pouch," coined from Late Latin marsupium "pouch, purse" (Classical Latin marsuppium), from Greek marsipion, diminutive of marsipos,marsippos "bag, pouch, purse," a word of foreign or Pre-Greek origin. As a noun, "a marsupial animal, an implacental didelphian mammal," from 1805.
nocturnal, omnivorous American marsupial mammal, c. 1600, from Powhatan (Algonquian) opassum, "equivalent to a proto-Algonquian term meaning 'white dog'" [Bright]. The colloquial form is possum (q.v.).
American marsupial mammal, 1610s, shortened form of opossum (q.v.). It is nocturnal, omnivorous, and when caught or threatened with danger feigns death; hence the phrase play possum "feign death when threatened," attested by 1822.
"large marsupial mammal of Australia," 1770, used by Capt. Cook and botanist Joseph Banks (who first reported the species to Europeans), supposedly representing a native word from northeast Queensland, Australia, but often said to be unknown now in any native language. However, according to Australian linguist R.M.W. Dixon ("The Languages of Australia," Cambridge, 1980), the word probably is from Guugu Yimidhirr (Endeavour River-area Aborigine language) /gaNurru/ "large black kangaroo."
In 1898 the pioneer ethnologist W.E. Roth wrote a letter to the Australasian pointing out that gang-oo-roo did mean 'kangaroo' in Guugu Yimidhirr, but this newspaper correspondence went unnoticed by lexicographers. Finally the observations of Cook and Roth were confirmed when in 1972 the anthropologist John Haviland began intensive study of Guugu Yimidhirr and again recorded /gaNurru/. [Dixon]
Kangaroo court is American English, first recorded 1850 in a Southwestern context (also mustang court), from notion of proceeding by leaps.