How did a pattern of dots printed on fabric end up being called polka dots?
It dates back to the mid to late 19th century, when the dance, the polka, was popular, and businessmen attempted to cash in on the craze by adding "polka" to the names of all sorts of products, ranging from socks, hats and curtains to dotted fabrics. The latter outlived the fad, and the rest disappeared.
No winner this week (Beckles you were so close!).