The British vet and writer Alfred Wight is best known for his series of semi-autobiographical stories written under the pen name James Herriot, recounting details of his experience as a country vet in North Yorkshire. In these books, he himself appears as James/Jim Herriot, rather than his real name of Alfred/Alf Wight, and his friends Donald and Brian Sinclair appear as Siegfried and Tristan Farnon.
The name James Herriot apparently comes from a Scottish goalkeeper whom he saw on television. What about the names Siegfried and Tristan Farnon? Where did these names come from and why?