In fairness, this is from Wikipedia:

The immigration records list his name as Friedr. Trumpf, but sources including the genealogy organization FamilySearch, a genealogist at About.com, and the 2013 book America's Obsessives concluded that both his father and his aunt's surnames were Trump.[16][17][18] According to the German Gesellschaft für Computergenealogie, Trump's earliest known male ancestor was Johann Paul Trump (1727-1792) in Bobenheim am Berg.[5] The story of an itinerant lawyer Hanns Drumpf presented by Gwenda Blair in her book The Trumps (2000) who settled in Kallstadt in 1608 and whose descendants changed their name from Drumpf to Trump during the Thirty Years' War of the 1600s[19][20][21] could not be substantiated and is not in accordance with the data provided by the German genealogists.[5] Journalist Kate Connolly, visiting Kallstadt, found several variations in spelling of the surname in the village archives (including Drumb, Tromb, Tromp, Trum, Trumpff, Dromb) but her article does not note "Drumpf".[22]