ציטירנדיקער פּירוש אויף בראשית 46:13

And of the sons of Issachar: Tola, and Puah, and Jashub, and Shimron In the Pentateuch (Gen. 46:13) it is written: “and Job.” Job was his name [originally], but since they settled themselves (נִתְיַשְּׁבוּ) to learn Torah, as it is written (below 12:33): “And of the sons of Issachar, who possessed understanding of the times,” he merited and was called Jashub (יָשוּב).

לישוב, he is identical with Yov (in Genesis 46,13) in that one ש was added to him from the two ש of his father (יששכר), and therefore, (the 2nd Shin) is not read in his father's name.

This is Yov… In Parshas Vayigash (Bereishis 46:13). Rashi explains in Divrei Hayomim I (7:1) that he was [really] called Yov, but since they settled down to learn Torah, as it is written (ibid. v.12), “From the sons of Yissachar there were those who had understanding of the times” he merited to be called “Yashuv” (lit. "settled").