Cullen is a traditional Irish surname that means "holly tree" in Gaelic. It is often used as a first name for boys and has a strong, masculine sound to it. People with the name Cullen are generally known for their loyalty, dependability, and strong sense of duty. They are often seen as protective, caring individuals who are always there for their friends and family. The name Cullen has also gained popularity in recent years due to its association with the popular "Twilight" series, where one of the main characters is named Edward Cullen.