We have already seen a double etymology given for the name Ishmael (#37), and likewise we will encounter many others. Here 2 traditions attempt to provide an explanation for the origin of Isaac’s name, which is built on the verb shaq—“to play,” to rejoice over,” or “to laugh.”
One tradition infers the reason for the child’s name by indicating that Sarah laughs when Yahweh—a stranger and a traveler to her—pronounces that she, who is past menopause, will conceive a son (18:11-12). This explanation finds itself in a passage whose features have already been identified as belonging to the Yahwist (#40).
Yet the other tradition, P, in keeping the figure of Abraham central, attributes the origin of Isaac’s name to the fact that Abraham laughed: “And Abraham fell on his face and laughed and said in his heart: ‘Will he be born to someone who’s a hundred years old!? And will Sarah, who’s ninety years old, give birth?’” (17:17). In other words, when the later Priestly writer retold this story, he told it in a manner that suited his particular views and interests.
The Elohist tradition may additionally be proposing yet another etymology, the one associated with the verb’s other meaning, “to play.” “But Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, playing (yitsaq) with her son Isaac” (Gen 21:9). At any rate, it’s certainly a pun on his name.
It was not uncommon to preserve variant etymological traditions. Stories and traditions were told and retold from generation to generation and often with slight variations or modifications, and these variations were often shaped by the concerns of the reciter or the community for which they were intended. See Stories.