Judah is Leah's fourth son: "this time I will praise G-d," she says, and she stopped bearing (Genesis 29:35). The name comes from hoda'ah, praise and acknowledgment. After three names that spoke of her husband, Leah names a son while turning to G-d.
Jacob takes up the name: "Judah, you, your brothers shall praise you; your hand shall be on the neck of your enemies; your father's sons shall bow down to you. A lion cub is Judah; from the prey, my son, you have risen; he crouches and lies down like a lion, like a lioness: who will rouse him?" Then: "the scepter shall not depart from Judah, nor the lawgiver's staff from between his feet, until Shiloh comes, and to him shall be the obedience of peoples" (Genesis 49:8 to 10). The one named with praise is praised in turn.
Moses prays for him: "Hear, O G-d, the voice of Judah, and bring him back to his people; let his hands fight for him, and be a help to him against his adversaries" (Deuteronomy 33:7). Rashi reads in it the prayers of the kings of Judah, David, Solomon, Asa, Jehoshaphat and Hezekiah; he also notes that Moses places Judah right after Reuben, because both acknowledged their fault.
On the breastplate his stone opens the second row: the nofekh (Exodus 28:18), under his name in the Targum attributed to Jonathan. It is often rendered as carbuncle or turquoise; the identification remains uncertain. In the desert Judah leads the eastern camp, with Issachar and Zebulun, and sets out first (Numbers 2:3 to 9). Ibn Ezra reports that a lion was on his banner, "for Jacob compared him to a lion." Ramban explains that he is in the east because he is the leader who goes at the head, and the Midrash he cites sees there kingship facing the east, whence light comes.
According to the order of the banners, Judah receives Nissan, the month of the letter Heh (Sefer Yetzirah 5:2); in the Vilna Gaon's version, Heh rules over speech. The Bnei Yissaschar recalls that Nissan is "the first of the months" (Exodus 12:2), the king of months, and that it belongs to Judah, "from whom comes the stem of kingship." The Shem MiShmuel attributes this order to the Ari. According to the order of birth, Nissan would go to Reuben.
Keep this: in Judah, kingship begins with a thank you. The mother praises, the brothers praise, and the first camp sets out behind the one whose name is acknowledgment.