Polka dots are evenly spaced circular spots printed, woven in, embroidered or flocked over fabric. The pattern was named in the late 19th century, derived from the popularity of the polka at the time. The dance gave its name to a variety of things during that period.
Dots about pinhead-sized are called pin dots, and large dots are called coin dots. Pin dots can be called dotted swiss, particularly when they are white-on-white.