Geronimo

Geronimo was a Native American friend of the Doctor's, also known as Goyaale (the One Who Yawns). (PROSE: The Hopes and Fears of All the Years) The Doctor knew him as early as his eighth incarnation.

It occurred to the Eighth Doctor that Geronimo would have been puzzled to know he would be remembered mainly by people who were about to fall from a great height. (PROSE: The Shadows of Avalon) The Eighth Doctor joked to Charlotte Pollard that Geronimo taught him the greeting "". (AUDIO: Storm Warning)