Background is helpful a lot of times. In some cultures, last name is determined by birth status. Noble born people would have titles and often would get their family name as well.
Scottish - Mac or Mc - like MacArthur likely the son of Arthur or a clan name
Germany - Von - Between first and last names, only used by nobles means from as in a noble from a particular regio.
Arabic - Ab or Ibn - meaning "father of" and "son of" as in
abu-al-qasim muhammad ibn abd allh ibn abd al-mut-alib Al hashimi
Father-of-Qasim, Muhammad, son of Abdullah, son of Abdul Mutalib, the Hashimi"
Irish - O' - meaning of or from and referring to a town city or county. Sometimes referring to a parent
Norman - de - Some of the early Norman nobility arriving in England during the Norman Conquest differentiated themselves by affixing 'de' (of) in front of the name of their village in France.
The British and Germans have a history of creating family names from a variety of sources: Occupation, Physical Description, location (place names or geographical features), parents (father or mother), or even who you worked for.
"So, I'm creating a human warlock for an ongoing campaign and as per usual, one of the hardest parts of creation is coming up with a name. Hes an infernal warlock who weilds a scythe, and is a grizzled veteran, cigar smoking, combat magician type of guy. Any suggestions on coming up with a name for this guy?"
So, has he earned any titles from his "Grizzled Veteran" look?
Is he the illegitimate son of some noble?
Maybe he's the black sheep of a family of religious zealots?
Is he from a desert region?
Does he carry the Scythe because he used to be a farmer?
Did he actually make his "deal with the Devil" with a short dude that promised him a pot O' gold?
Does he roll his own Cigars, or does he have them shipped in from some small country where they are hand crafted just for him?
More detail would allow for a much more creative name. Or were you just looking for us to throw out suggestions?
Cause I'd go with Devin KilPatrick
and he's always hunting for a guy named patrick to kill.