A scab worker is a person who works during a strike or planned work stoppage, in violation of the strike. The term "scab" is a derogatory term used to describe such workers. The term has its origins in the Old Norse word for the hardened crust that forms around a wound, as well as to a disease affecting the skin of animals and plants. By the 1500s, scab was being used as an insult to refer to someone as a lowlife, scoundrel, or generally "contemptible person." Workers started to use the term as a pejorative in the late 1700s and early 1800s to refer to someone who refused to join a union or acted in a way that would undermine their fellow workers. The term has been used in the United States since 1806 to describe strikebreakers during a trial of striking bootmakers and shoemakers.