means A low-lying area of land that is saturated with water permanently or seasonally, supporting plants and wildlife adapted to wet conditions — marshes, bogs, swamps, and fens.

from A transparent compound of "wet" and "land," both rooted in Old English (wǣt and land). The word itself is a relatively modern joining, rising into common use as ecologists and conservationists in the 20th century needed a single neutral term to cover everything once dismissed as swamp, marsh, or bog — places long drained and feared before their value was understood.