Last names may have been around since 1000 AD, but not the same kind of last names we have now. Last names back then were not passed down as Family names. If your dad was named Erik (and you lived in scandinavia) then your last name would be Erikson--but your dad's last name might've been Hanson (Hans' son) People in other parts of europe were named for their occupation: Smith (blacksmith), Thatcher (some kind of farming duty), Tepes (impaler).
Tepes was not a name used by anyone...ever! The real dracula signed his name "Vlad Dracula" because his father was nick-named "Dracul". If Alucard was real, he would not have the name Tepes or Farenhiet. He was not Adrian the impaler, so no one would call him Tepes; and Farenheit is a German name.
The main problem here is trying to connect video games with reality. It just doesn't work. Don't try to analyze why certain fictional characters have certain names--it's all just made up!!