What is the origin of word marsupial?

The word "marsupial" has its roots in Latin. It comes from the word "marsupium," which means "pouch."

This is fitting considering the defining characteristic of marsupials is their pouch, a flap of skin on the belly of the mother where their young develop after birth.

The word "marsupium" was first used in scientific contexts in the 18th century to refer to this pouch. The word "marsupial" itself was adopted in the 19th century to describe animals possessing this feature.