A first or Christian name has been used since man was first able to communicate.
Surnames did not really catch on until the 12th century. The practice of referring to people by their surnames has dramatically decreased in the last 50 years in favour of using less formal first-names, or Christian names.
The change in Christian name usage began in America and reflected the move to equality between classes and sexes. Our first, or Christian name is what we are, now, commonly known by.