Adam Clarke on Deuteronomy 32:17

They sacrificed unto devils - The original word שדים shedim has been variously understood. The Syriac, Chaldee, Targums of Jerusalem and Jonathan, and the Samaritan, retain the original word: the Vulgate, Septuagint, Arabic, Persic, Coptic, and Anglo-Saxon, have devils or demons. The Septuagint has εθυσαν δαιμονιοις, they sacrificed to demons: the Vulgate copies the Septuagint: the Arabic has sheeateen, the plural of Sheetan, Satan, by which the rebellious angels appear to be intended, as the word comes from the root shatana, he was obstinate, proud, refractory, went far away. And it is likely that these fallen spirits, having utterly lost the empire at which they aimed, got themselves worshipped under various forms and names in different places. The Anglo-Saxon has devils.

New gods that came newly up - מקרב באו mikkarob bau, "which came up from their neighbors;" viz., the Moabites and Amorites, whose gods they received and worshipped on their way through the wilderness, and often afterwards.