I was surprised to find out ‘Luther’ is not Martin Luther’s original surname but ‘Luder’ is. The Greek word έλεύθερος that was the origin of his Latin name was Eleutherius. You can see ‘uder’ does not quite sound as good as ‘uther’. You can hear the sound of the Greek word here: click on the speaker sign to listen
I have read that in the fall of 1517 he changed his name. So what would make Luther get so fussy about his name so that he wanted it to match the original Greek more audibly?