Why do people have two names?

Answer 1

There was a time when people did not have two names. In the days of The Bible (about 5000 years ago), for example, it was common to refer to a person only by one name (Moses, Abraham, Miriam), although sometimes the person was identified by his or her parents' first name as well-- Joel, son of Pethuel, for example; or sometimes the person was identified by their city or ethnic group, such as Ruth the Moabite (she came from Moab).

Later, as society expanded, and nomadic people settled into stable communities, people began to be identified by their occupation: the word "Smith" for example, was a shortened form of "blacksmith," and Cooper was a name for a person who made barrels. In fact, some of today's last names come from those early days when one's occupation became a last name; and a number of last names are also related to the name of a family's ancestral town or village.

There are a number of sociological theories about why last names became necessary (some cultures still only use one name-- in Afghanistan, it is still common in some parts of the country), but most likely it had to do with the population continuing to grow and expand, making it essential to find new ways to tell people apart and differentiate them.

Answer 2

Parental choice or cultural traditions.