O'Connell was born in Los Angeles, California, on December 18, 2001. She is the daughter of actress and screenwriter Maggie Baird and actor Patrick O'Connell, both of whom are also musicians. Eilish is of Irish and Scottish descent. She was raised in Los Angeles' Highland Park neighborhood. She was homeschooled and her mother taught her and her elder brother Finneas O'Connell basics of songwriting. Eilish and Finneas had worked together on some music, while Finneas had been writing and producing his own songs and performing with his band. Eilish said Finneas and her mother inspired her to get into music. Their parents encouraged the siblings to express themselves and explore whatever they wanted, including art classes and acting. Eilish wrote her first "real" song at age 11 for her mother's songwriting class. The song is about the zombie apocalypse, inspired by the television series The Walking Dead from which she took script lines and episode titles that she added to the song as part of the assignment. Eilish had gone on some acting auditions, which she disliked. However, she enjoyed recording background dialogue for crowd scenes and worked on the films Diary of a Wimpy Kid, Ramona and Beezus, and the X-Men series. She performed at talent shows and joined the Los Angeles Children's Chorus at age eight.