Well, it has to do with the apparatus of a distiller, albeit a very old one I presume. Here:
feeverte.net/dicksdistillation.html
"This process of evaporating and condensing a liquid is called distillation; the apparatus is called a still or retort, and the coiled pipe is the "worm of the still," or the condenser."
This [Worm of the still] is a long tin pipe, bent in the form of a screw, and enclosed in a copper or wooden vessel full of cold water.