A teacake was a kind of cake. Kate Yates once purchased a teacake from a tea shop in Winchelham. (PROSE: I Am A Dalek)
Nardole claimed to the Twelfth Doctor that he was the only one in the TARDIS who knew where the tea cakes were. (TV: The Eaters of Light)
Behind the scenes[]
Teacakes are named such because they were typically served with tea.