The daughters of a New Hampshire poet say “The Big Bang Theory” stole their mother’s verses about a “soft kitty” for a lullaby that has become a staple of the television show.

A lawsuit against Warner Brothers, CBS and other media companies said that the poem was written by Edith Newlin, a teacher, in the 1930s and that it was published in 1937 in a book called “Songs for the Nursery School.”

Ellen Newlin Chase and Margaret Chase Perry, accusing the companies of copyright infringement, say permission was never sought from their mother before the words were used in several episodes of the comedy, about socially awkward scientists navigating the world with the help of an outgoing waitress neighbor.