The word opossum comes from Virginia Algonquian opassom or aposoum, generally translated as white animal or white beast — a reference to the animal's pale, whitish face. Captain John Smith recorded the word in 1612, making it one of the earliest Algonquian borrowings alongside moose, moccasin, and raccoon.
The Virginia opossum (Didelphis virginiana) holds the distinction of being the only marsupial native to North America. Its presence in North America puzzled European naturalists who encountered it — a pouched mammal in the New World, thousands of miles from the marsupial stronghold of Australasia. Modern biogeography explains this distribution through the ancient history of continental drift: marsupials originated in what is now South America, spread to Antarctica and Australia when these continents were connected, and later migrated north into North America when the Isthmus of Panama formed.
The informal shortened form possum (dropping the initial o-) has been standard in colloquial American English since the 18th century. This clipped form also gave rise to the idiom playing possum — pretending to be dead or inactive. Despite the phrase's implication of deliberate deception, the opossum's thanatosis (death-feigning) is actually an involuntary physiological response to extreme stress, not a conscious strategy.
When triggered by fear, the opossum enters a catatonic state: it collapses, its body goes rigid, its eyes glaze, its tongue protrudes, and it secretes a foul-smelling fluid from its anal glands that simulates the smell of decay. The response can last from minutes to hours. The animal has no control over when this state begins or ends — it is as unconscious during thanatosis as it appears to be.
In Australian English, possum refers to entirely different animals — the phalangers and their relatives, which are true Australian marsupials. Captain Cook's botanist Joseph Banks named them possums in 1770 because they reminded him of the American opossum, creating a linguistic connection between unrelated animals on opposite sides of the Pacific.