"agur": "gathered together," as in (Proverbs 30:1) "the words of "agur bin yakeh" (Solomon) the gatherer of wisdom." And (Psalms 55:16) "Let Him incite death against them; let them go down alive into Sheol. For evils are stored up ('b'meguram') in their midst."
(Devarim, Ibid.) "lest their oppressors estrange them": When Israel is in distress, the nations estrange them, as if they did not exist in the world. And thus we find that when Israel wanted to flee to the north they handed them over (to their foes), viz. (Amos 1:9) "Thus said the L-rd: For three transgressions of Tyre, etc." When they wanted to flee to the south, they handed them over, viz. (Ibid. 6) "Thus said the L-rd: For three transgressions of Azza, etc." When they wanted to flee to the east, they handed them over, viz. "Thus said the L-rd: For the three transgressions of Damascus, etc." When they wanted to flee to the west, they handed them over, viz. (Isaiah 21:13) "The prophecy for Arav: In the forest, in Arav shall you lodge, O caravans of the Dedanites, etc."