Tony Stark’s AI assistant introduced in Avengers: Age of Ultron is F.R.I.D.A.Y. Tony activates her after Ultron attacks and seemingly destroys J.A.R.V.I.S., his longtime digital assistant.
F.R.I.D.A.Y. helps operate Stark’s armor and supplies battlefield information, continuing the role J.A.R.V.I.S. had performed. In the Marvel Cinematic Universe, she is voiced by Irish actor Kerry Condon and has an Irish accent.
A common mix-up is EDITH, another Stark-created artificial intelligence introduced much later in Spider-Man: Far From Home. Karen is the assistant system in Spider-Man’s upgraded suit, while J.A.R.V.I.S. is not simply renamed: his consciousness becomes part of Vision after the events involving Ultron and the Mind Stone.
The name also has a literary connection. “Friday” refers to the loyal companion of Robinson Crusoe in Daniel Defoe’s 1719 novel, which fits the traditional expression “a girl Friday” for a highly capable assistant.