atheroma (n.)

"encysted tumor," 1706, medical Latin, from Greek atheroma, from athērē "groats, porridge," in reference to the matter inside; a word of unknown origin. It is sometimes said to be perhaps related to athēr "chaff," but Beekes finds this "neither formally nor semantically plausible." Pliny calls it an Egyptian word. For the ending, see -oma. Related: Athermatous (1670s).