Charles Ellicott Commentary Jeremiah 31:39

"And the measuring line shall go out further straight onward unto the hill Gareb, and shall turn about unto Goah." — Jeremiah 31:39 (ASV)

The hill Gareb ... —Neither of the two localities named is mentioned elsewhere, and their position is accordingly a simple matter of conjecture. The name of the first, as signifying “the leper’s hill” (the term includes leprosy as well as other skin diseases, Leviticus 21:20; Leviticus 22:22), probably indicates a position outside the walls assigned as a dwelling for people suffering from that disease. Some think this position corresponds with the hill on the north side of Jerusalem that Josephus describes as Bezetha (Wars, v. 4, § 2). Others, however, assign its position to the south-west corner of the walls.

The name Gareb appears in 2 Samuel 23:38 as belonging to one of David’s thirty heroes, but there is nothing to connect him with the locality. Goath is a word of doubtful etymology. Some scholars (Hitzig) interpret it as “high-towering,” and refer it to the height overlooking Kidron, later surmounted by the tower Antonia. The Targum, however, paraphrases it as “the pool of the heifers,” and connects the name with the verb for the lowing of that animal. By some writers it has been identified with Golgotha, but both topography and etymology are against this view.