Nom De Mom

Many years ago, Alice Troper married Bob Laconic and changed her last name to his. Their daughter Carol, however, opts to take Alice's last name instead of Bob's.

Reasons for Carol Troper's use of her mother's maiden name vary. Maybe she had a huge falling out with her dad, maybe she's challenging traditional gender norms, or maybe she just doesn't like Bob's last name.

As a general rule of thumb, this trope should apply to children who originally went by their father's last name and made the change later, whether self-motivated or otherwise.

This trope does not apply to illegitimate children who use their mother's name because they can't go by their father's--the use of the mother's name should be a choice, not a necessity.

Examples of Nom De Mom include:

Anime and Manga

In the original Japanese version, of Yu-Gi-Oh!, Katsuya Jounouchi's sister Shizuka does this, taking her mother's maiden name Kawai. Their parents are divorced and Shizuka lives with her mother. The 4Kids dub averts this by having Serenity still use Wheeler.
Portgas D. Ace of One Piece uses his mother's name instead of his father's, feeling he owes her greatly while the fact of who his father is has caused him nothing but grief.
In Code Geass, Lelouch Lelouch vi Britannia and Nunnally vi Britannia go by their deceased mother's maiden name of Lamperouge to disguise their identities.
- And from the same series, Kallen goes by her mom's Japanese name, Kozuki, when she's working with the Rebellion rather than her father's Brittanian name, Stadfeldt. This serves the dual purpose of disguising her identity and showing that she identifies more with her mom's side of the family, as well as a form of rebellion since being a Brittanian carries many more rights than being an "Eleven" or Japanese person.

Comic Books

Rachel Grey in X-Men, formerly Rachel Summers. (Daughter of an alternate future Jean Grey and Scott Summers, at least by what's in print.)

Film

The Reveal at the end of Down Periscope is that Brad Stepenak is actually Admiral Wilson's son. He uses his mother's name to avoid patronage and to rebel against his father.
In Live Free or Die Hard, John McClane's daughter uses her mother's maiden name Genero to distance herself from her father; a Call Back to the original, where his wife had done the same after she moved to a new job in California (that is, she changed it to Genero, not her mothers maiden name).
In Prometheus, it's implied that a falling out with her father, Peter Weyland made Meredith Vickers not use his name.

Literature

In the Vorkosigan Saga, Miles Vorkosigan uses his mother's maiden name in his secret identity as Admiral Miles Naismith. Per Naismith's cover story he is a clone of M. Vorkosigan, hence of the same genetic offspring and hence legally entitled to the name. Additionally, even in his non-cover identity Miles Vorkosigan's middle name is Naismith, as a substitute since his paternal grandfather forbade that he should be named after him.
In the Cal Leandros books, brothers Cal and Niko keep their mother's name, not because they got along with her, but because Cal's father is a nameless monster and Niko didn't meet his until he was an adult.

Live Action TV

In the pilot episode of That Girl Anne Marie considers using her mother's maiden name as her last name because - per her agent - everyone thinks "Marie" is her middle name. "Anne Marie what?"

Video Games

In Final Fantasy VIII, Rinoa Heartilly goes by her mother Julia's maiden name to disassociate herself from her father, Fury Caraway, who is a general in the military of the same nation she's a member of La Résistance against.
- Widespread Final Fantasy VIII Fanon also holds that Squall Leonhart's surname comes from his mother Raine, since his father's surname turns out to be something different, but Raine's maiden name is never given so there's no way to confirm the theory. Quite possibly Edea made up the surnames for all the orphans under her care.
A variation in Tales of the Abyss where Guy Cecil uses a slightly different version of his mother's maiden name as a cover for his true heritage.
In Alpha Protocol, Madison Saint James uses her mother's maiden name after having a falling out with her father, Alan Parker.
Caren Ortensia in Fate/hollow ataraxia uses her mother's surname because her father, Kirei Kotomine essentially abandoned her after her mother died.

Web Comics

Abstract Gender: A couple of years after Ryan was born, his father left...but before going, legally changed his son's last name to his mother's maiden name.

Web Original

Although her father is Taiyang Xiao Long, Ruby from RWBY uses her mother's last name, "Rose".

Western Animation

In The Simpsons, when Lisa learns that Homer had been betting against her on crossword competitions, she starts going by Lisa Bouvier.
In Young Justice, Word of God says that Cheshire/Jade Nguyen uses her mother's maiden name because of her issues with her father, Sportsmaster/Lawrence Crock.