There are a few theories about why the Romans called them Picts:
* Body paint: The most widely accepted theory is that the Picts painted their bodies for war and ritual purposes. This practice was common in many ancient cultures, and evidence suggests that the Picts did use body paint and tattoos.
* Distinctive appearance: It's possible that the Picts had a distinct physical appearance that differentiated them from other groups, possibly related to their hairstyles, clothing, or facial markings.
* Propaganda: The Romans might have used the term "Picti" as a form of propaganda to portray the Picts as savage and primitive.
However, it's important to note that the Picts themselves never called themselves "Picts." The term "Picti" was an external label given to them by the Romans, and they referred to themselves with their own names, which we don't fully understand.
The origin and meaning of the term "Picti" remains a subject of debate among historians and archaeologists, but the association with body paint and tattoos is the most plausible explanation.