Literally, it means to take a course opposite the apparent motion of the sun viewed from the Northern Hemisphere. Widdershins is cognate with the German widersinnig, i.e., “against” + “sense”. The opposite of widdershins is deosil, or sunwise, meaning “clockwise”.
This is a big part of why I love them so much. Hardly a week goes by that I don’t think of the “boots theory of socio-economic unfairness” from Men at Arms!