Why is Sigourney Weaver's stage name called "Sigourney Weaver" since her real first name is Susan?

Born in 1949, she changed her name in 1963 to "Sigourney", after the character "Sigourney Howard" in F. Scott Fitzgerald's "The Great Gatsby" (her
own birth name, Susan, was in honor of her mother's best friend,
explorer Susan Pretzlik).

FROM BOOK:

“I’ve just heard the most amazing thing,” she whispered. “How long were we in there?”



“Why, about an hour.” “It was — simply amazing,” she repeated abstractedly. “But I swore I wouldn’t tell it and here I am tantalizing you.” She yawned gracefully in my face: “Please come and see me. . . . Phone book . . . Under the name of Mrs. Sigourney Howard . . . My aunt . . .” She was hurrying off as she talked — her brown hand waved a jaunty salute as she melted into her party at the door.''