vlad got his nickname, 'tepes' (the impaler) after he died. when he was alive he was voyvode vlad, son of vlad dracul. based on his father's name he was occasionally called 'draculea' (which sounds like dracula). dracula was a name associated with him before bram stoker, although that is where the link between the vampire and the real person ends.
i've read on many internet sites that dracula means son of dracul. but i cannot explain it gramatically. maybe that's how people talked in the 15th century. but when family names spread in romania (around the 19th century, before that it was x son of y...) the common ending to the father's name was 'escu' (there are many escus nowadays in romania): popescu, ionescu, stefanescu.i have never heard of 'the son of stefan' turning into 'stefana'. so i don't know exactly how viable the explanation is.
however, dracula does come from vlad dracul, there's no doubt about it. he was called dracula too, on occasion, and when his son ruled he was occasionally called 'dracula the young'. vlad the impaler's brother, radu, was also called 'dracula the young'. the descendants of vlad dracul were called 'draculesti'. there's a whole family of draculas out there
. (vlad tepes is the most famous, of course).
about vlad tepes, yes, he was a sadist by today's standards. but please remember that he grew up in a turkish prison. his father was killed by his ally, john hunyade. his older brother was burried alive. he lived in a time soon after joan of arc was burnt alive. he lived in an insecure country in which from 1418 (death of his grandfather, mircea the old) and 1448 (the first time he came to the throne) there were many rulers: mihai 1st, dan 2nd, alexandru aldea, vlad dracul, vladislav 2nd. i think there were more (as i said, i don't have a book of hand) but even if it was only them, that's 5 rulers in 30 years! it was a most insecure time. when he came to the throne, there were 3 other different pretenders out there available for whoever was upset at vlad for any reason. the country was in ruin, it was filled with thieves, beggars, the country people were burdened by heavy taxes set to pay the turkish tribute. the boyars were like kings on their domains.
i am not trying to defend him, but in 6 years he managed to get the country in shape. there was reason to his madness.