Eleven uses the nickname “Papa” for Dr. Martin Brenner. The name reflects the complicated parental role Brenner imposed on her while controlling her life at Hawkins National Laboratory.
Brenner abducted Eleven as a child and raised her among other gifted test subjects. Although he presented himself as a father figure, he subjected the children to isolation, surveillance, psychological manipulation, and dangerous experiments designed to develop their abilities. Eleven’s memories repeatedly associate him with the Rainbow Room, the laboratory’s numbered children, and the command structure surrounding the experiments.
“Papa” is therefore not a warm family nickname in the ordinary sense. It carries both familiarity and coercion. Eleven uses it because Brenner encouraged the children to see him as a parental authority, even while he treated them as research subjects. She also uses “Papa” in moments when she is frightened, conflicted, or seeking recognition from him.
Other adults have different relationships with Eleven. Dr. Sam Owens tries to protect her, while Jim Hopper eventually becomes her genuine adoptive father. By season 4, Eleven recognizes more clearly that Brenner’s claimed affection does not erase the harm he caused, and she refuses to forgive him before his death.