Follis (ball)

Follis (a term used in Ancient Rome), or Ball of wind (pilota de vent in Catalan), a term used in the 15th and 16th centuries in Spain and Italy, was a hollow ball inflated with air under pressure able to jump and bounce when impacting at a certain speed with any solid body. Different types of balls of wind were commonly used to play a variety of ball games that were popular in that particular period of time.

Today, although many of the existing balls are inflated with air, the modern name is simplified to "ball" regardless of the system.