Langdon, Langston, Landon, Langton, Langthorne are really all the same name. It is just the way you say it according to accent and geography. Even with the same spelling Langdon will be pronounced differently in New England and Texas. Archbishop Stephen Langton who wrote Magna Carta is recorded in papal documents as Stephen Langdon. So if you want to discover your British origins get Y testing and Big Y testing.

There are also more extreme corruptions to Longstaff, Longhorn, Leyton, Luton, Lenton and others.