Shelly (The Playthings of Fo)

Shelly was a human companion of the First Doctor who travelled in the TARDIS with Dr Harroll Strong, his two children, Jack and Dot, and two unrelated men, Chertzog and Hill. He was a young, broad man with blond hair. (PROSE: The Devil-Birds of Corbo, The Playthings of Fo)

Behind the scenes
Due to the way the other male companions in these two stories are referred to, Shelly is almost certainly this character's surname.