Keluaran 9:9-10

9:9 It will become fine dust over the whole land of Egypt and will cause boils to break out and fester ¹  on both people and animals in all the land of Egypt.” 9:10 So they took soot from a furnace and stood before Pharaoh, Moses threw it into the air, and it caused festering boils to break out on both people and animals.

[9:9]  ¹ tn The word שְׁחִין (shÿkhin) means “boils.” It may be connected to an Arabic cognate that means “to be hot.” The illness is associated with Job (Job 2:7-8) and Hezekiah (Isa 38:21); it has also been connected with other skin diseases described especially in the Law. The word connected with it is אֲבַעְבֻּעֹת (’ava’bu’ot); this means “blisters, pustules” and is sometimes translated as “festering.” The etymology is debated, whether from a word meaning “to swell up” or “to overflow” (W. C. Kaiser, Jr., “Exodus,” EBC 2:359).