Occurs only in connection with the sixth plague of Egypt (Ex. 9:9, 10). In Deut. 28:27, 35, it is called "the botch of Egypt." It seems to have been the fearful disease of black leprosy, a kind of elephantiasis, producing burning ulcers.
violent ulcerous inflammations, the sixth plague of Egypt, (Exodus 9:9,10) and hence called in (28:2...
William Smith's Bible Dictionary