The word "of" is a preposition commonly used in English. It indicates a relationship between two entities, often expressing possession, origin, or the concept of belonging. For example, it can show that something belongs to someone or that something is made from a particular material.
The word "of" originates from Old English "of," which meant "away from" or "from," and is related to similar words in other Germanic languages, showing a long history of indicating relationships between entities.