The common moorhen (Gallinula chloropus), also known as the waterhen or swamp chicken, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World. The name mor-hen has been recorded in English since the 13th century. The word moor here is an old sense meaning marsh. the species is not usually found in moorland. An older name, common waterhen, is more descriptive of the bird's habitat. A "watercock" is not a male "waterhen" but the rail species Gallicrex cinerea, not closely related to the common moorhen. "Water rail" usually refers to Rallus aquaticus, again not closely related. The scientific name Gallinula chloropus comes from the Latin Gallinula (a small hen or chicken) and the Greek chloropus.
