Greek λοιμός, Middle Persian rēm, and the Avestan root rai̯-

The Greek name of the plague has not received a satisfactory etymological explanation so far. On the other hand, the largely accepted hypothesis that the Middle Persian noun rēm ‘dirt, impurity’ is derived from a verbal base meaning ‘defecate’ is, in fact, problematic. The present paper aims to show that MPers. rēm and Gk. λοιμός can be viewed as reflexes of a PIE stem *loi̯-mó- indicating a ‘polluted (and polluting) substance’ and that the Avestan root rai̯-, probably connected with MPers. rēm, must have had the generic meaning of ‘to dirt, to pollute’.