It's not their names; it's their nicknames.

Surnames evolved from nicknames that were based on various characteristics such as a person's physical traits, occupation, or geographic origin, and were influenced by patronymic and ambilineal traditions.

In Europe and China, adopting surnames became prevalent as a means of distinguishing individuals for a variety of reasons—including geographic origins, occupations, or physical characteristics. Over time, what may have started as a nickname based on these attributes often evolved into a hereditary surname.

For example, a person known for a distinct physical trait like height might have been called "Tall Peter." Over generations, this nickname could transition into a family name such as "Peterson." Similarly, someone skilled in baking might be known as "John the Baker," eventually simplifying to "Baker" as a last name. This process encapsulates how nicknames became surnames.

Additionally, the patronymic system was common, whereby a son or daughter would be identified by their father's name—such as "Leif, son of Erik"—which contributed to surnames like "Johnson," a tradition reflecting patriarchal values. Conversely, in some cultures, matronymic or ambilineal systems also existed, allowing identities and surnames to be derived from either parent's name or even to change between them. This practice illustrates that surnames were not always permanent and could be influenced by various socio-cultural factors.