rheumy and unpurged air "Rheum" meant, according to the Oxford English Dictionary, "Watery matter secreted by the mucous glands or membranes, such as collects in or drops from the nose, eyes, and mouth, etc., and which, when abnormal, was supposed to cause disease . . . ." It was also thought that night mists contained rheum which could make a person sick; the air wasn't safe until the warmth of the sun had purged the rheum.