Lots of welsh forenames became surnames, because the usual convention was to refer to "x son of y", so "Richard ap Richard" was rewritten as "Richard Richards" or "Richard Pritchard".
In England we have a common situation where a surname is used as a given name, often because it was the maiden name of a grandmother. Thus I have a "Bullough Bullough", as well as a "Bella Bullough". Bella was short for Arabella, but in 1861 the enumerator wrote it down as "Bellow". I'm not sure if it matched her voice!