In Europe during the Middle Ages and Renaissance dots on clothing were considered impurities and associated with uncleanliness and disease (reminiscent of the dots seen in smallpox and other infectious illnesses). Polka dot popularity in fashion began in nineteenth century Germany. The word polka in polka dots came from the Czech dance by that name which was fashionable at the time. Placing dots on clothing were facilitated by the development of the sewing machine. Dots continued to be popular in clothing, especially in casual and summer dresses and swim-suits in the twentieth century. Dots are now also popular on beads in jewelry. An example can be seen in the above picture of a bracelet featuring a dotted lampwork glass bead which can be purchased at SILVER VIKING BLUE BEAD WHITE DOT BRACELET (beadshaper.com) .
If you want to read more about the history of polka dots, I would recommend clicking the following 2 sites:A Comprehensive History of Polka Dots Throughout the Centuries (cosmopolitan.com)