"Hush, Little Baby, Don't Say a Word" is the first line of a lullaby traditionally attributed to Mother Goose. In the lullaby, a father pledges to buy his baby all sorts of things, promising that if something happens to each gift, he'll buy another.
Like all lullabies, this one is meant to provide a child with a sense of comfort and security. In the last line, the father reassures the baby that even if all these gifts are broken or ruined, "You'll still be the sweetest little baby in town!" The baby's identity isn't in her external circumstances—it's all inside her—and in this way, the lullaby reflects both the relationship between Toswiah/Evie and Daddy and the truth about her own identity that Toswiah/Evie comes to.