What is a "tam-o'-shanter"?

A tam-o'-shanter is a Scottish woolen cap that typically has a pom-pom or tassel on top. It is named after the eponymous poem by Robert Burns and has a distinctive shape, with a flat crown and a slightly sloping brim that is often embellished with a decorative band or ribbon. Tam-o'-shanters are commonly worn by men and women, and they are especially popular in Scotland and other parts of the United Kingdom. They can be worn for both casual and formal occasions and are often associated with traditional Scottish dress.