The English were already using inherited family names in the 1300s. By the 19th century, the use of a non-inherited byname meant literally would be so unusual, it would be written up in every onomastic and genealogical journal.
Alice was named Blackmore because her father was named Blackmore. He was named Blackmore because his father was named Blackmore. And so on and so forth for dozens of generations, until you get to some progenitor in the Middle Ages who was called Blackmore because of his swarthy complexion.