Midrasch zu Bamidbar 10:28

Now Jethro heard (Exod. 18:1). Jethro was known by seven names. He was called Jethro (yitro) because he added (yater) a chapter to the law, that is, the chapter dealing with judges. He was called Hobab (hobab) because he loved (hiba) the law. When he came to the Holy Land, they offered him the fields of Jericho, but he said: “I brought none of my possessions with me, and I abandoned all I owned in order to study the Torah, shall I now sow and reap when I should be studying Torah?” They told him: “There is a man studying the law in a certain area that is in a desolate place in the desert, and it lacks even wheat.” When they heard this, they went there, as it is said: And the children of the Kenite, Moses’ father-in-law, went up out of the city of the palm trees with the children of Judah, unto the wilderness of Judah, which is in the south of Arad; and they went and dwelt with the people (Judg. 1:16).⁷See Ginzberg, Legends of the Jews 3:76. The descendants of Jethro devoted themselves to Torah study. They went there and found Jabez sitting in the house of study, and the priests, the Levites, and the rulers were sitting with him, and all the Israelites were sitting there. And so they said to him (Jabez): “We are converts, how can we sit there among them?” Thereupon they seated themselves at the entrance to the school and listened and learned, as it is said: The families of scribes that dwelt at Jabez: the Tirathites, the Shimeathites, the Succathites. These are the Kenites (I Chron. 2:55). They were called tiratim (Tirathites) because they sat at the gate (sha’ar), shime’atim (Shimeathites) because they listened (from shama, “to hear”) and learned, and sukhatim (Succathites) because the Israelites made it clear to them (from mesakhim, “looked after them”). Another explanation (of Tirathites). Whenever the Israelites were confronted by danger they would blow (matri’in) their shofars, and they (Kenites) would hear them.