Why do people have bobbles on the top of their arms?

The "bobble" on the top of the arms, commonly referred to as "triceps brachii," is a muscle that contributes to the shape and contour of the upper arm. It is primarily involved in the extension of the elbow and plays a role in various arm movements. Genetics, body fat percentage, and muscle development can influence the prominence of this area, causing variations in appearance among individuals.