“Was not your sister Sodom a byword (‘report, news item') in your mouth in the day of your pride, before your wickedness was discovered? Just as the time of the reproach of the daughters of Aram and of all who are round about her, the daughters of the Philistines who do despite to you round about. You have borne your lewdness and your abominations, says Yahweh.”
The idea here is that they had once used the name of Sodom as a byword for sin, until things changed when their own wickedness was uncovered, and now similarly they are being made a byword for sin by the people of Aram (Syria) and by the Philistines who are round about them. Thus they are receiving the consequence of their dreadful behaviour. They have replaced Sodom as the epitome of lewdness.