Albert Barnes Commentary 2 Samuel 17:18

"But a lad saw them, and told Absalom: and they went both of them away quickly, and came to the house of a man in Bahurim, who had a well in his court; and they went down thither." — 2 Samuel 17:18 (ASV)

Bahurim - See the marginal reference. They were not all Shimeis in Bahurim.