The name is from Algonquian wapathemwa, not Greek or Latin, so the plural is opossums, not opossa.
The Virginia Opossum is noted for its reaction to threat, which is to feign death. This is called "playing (o)possum".
Though opossum is often pronounced, and even spelled possum, the latter word actually refers to various distantly related but broadly similar animals of magnorder Australidelphia, that are native to Australasia and are an introduced pest in New Zealand. See possum.
See also: Pogo