Source please ? As far as I can tell , both he and his father were born Trump . Go back a few generations further and maybe it was Drumpf , but many , MANY immigrants changed their names when coming over first names and last names . It ' s not like it says Drumpf on his birth certificate and he ' s just going by a name he prefers . Let ' s say I ' m completely wrong and his birth certificate and drivers license both read Donald Drumpf he is still using the last name Trump in all social settings . Referring to him by a name popularized for the purpose of mocking him damages your credibility and is schoolyard antics , not legitimate criticism and it absolutely does damage the credibility of anything you say next .