古英語のmos, marsh, bogから、PIE*meusのmoisture, moistureが語源。
Selden Moset te Marbelston tat men ofte treden. ["Piers Plowman," 1362]All the Germanic languages have the word in both senses, which is natural because moss is the characteristic plant of boggy places. It is impossible to say which sense is original. Scott (1805) revived 17c. moss-trooper "freebooter infesting Scottish border marshes."