Flannel is a warm, soft cotton or wool fabric. Plaid work shirts are commonly made of flannel.
Flannel has been around since the 1700s, when it was created in Welsh textile mills. Pants made of flannel became popular throughout Britain by the early 20th century, particularly in sports like cricket — these trousers are often called flannels. Another kind of flannel is a washcloth or cloth for cleaning. The word flannel is probably related to the Welsh gwlanen, "woolen cloth."