Etymology: In Middle English the word was ekename (from the verb to eke, "enlarge"; compare Swedish öknamn). Later, an ekename developed into a nickname.
Lots of things have nicknames
Types of personal nickname:
1. A nickname may relate directly to a person's first name. Examples:
2. A nickname may relate directly to a person's surname. Examples:
3. It may also relate indirectly to a surname. Examples:
4. A nickname may relate to the person's job. Examples:
5. It may relate (offensively or otherwise) to a person's nationality or place of origin. Examples:
6. It may relate to a person's physical characteristics. Examples:
7. It may relate to a person's character. Examples:
8. It may relate to a specific incident or action. Example: Capability Brown was so called because he used the word "capability" instead of "possibility".
9. It may compare the person with a famous or fictional character. Examples:
10. A famous person's nickname may be unique to them:
11. A person's nickname may have no traceable origin. For example a person named "Harold" may be nicknamed "Fred" for no apparent reason, or a man who was named after a relative may ask his friends to call him "Chip" to avoid confusion.
much to add here, this is a start