1911 Encyclopædia Britannica/Dowser and Dowsing

DOWSER and DOWSING (from the Cornish “dowse,” M.E. duschen, to strike or fall), one who uses, or the art of using, the dowsing-rod (called “deusing-rod” by John Locke in 1691), or “striking-rod” or divining-rod, for discovering subterranean minerals or water. (See Divining-Rod.)