Katherine is a Greek name which means “pure”.
Kate’s name may be derived from that of a character from John Steinbeck’s Nobel Prize-winning novel East of Eden. Catherine is one of the main antagonists and, like Kate, sets her parents’ home on fire as a young girl (killing both of them, as opposed to Kate who just kills her step-father) and spends most of her life from that point forward running from the law. Catherine later changes her name to Kate to further avoid detection
Kate has been referred to as or used the aliases Katherine Ryan, Katherine Dodd, Joan Hart, Maggie Ryan, Annie, Lucy, and presumably lived under the name Monica Callis during her marriage. Her father, Tom Brennan, and Jacob called her Katie. Her mother called her Katherine. Sawyer almost always calls her Freckles, but occasionally calls her Kate during particularly emotional or tense conversations.
"Joan Hart" is a reference to Melissa Joan Hart, who starred in the television show Sabrina the Teenage Witch. Her co-star, Beth Broderick (“Aunt Zelda”), plays Kate’s mother, Diane Janssen.