The idea of entropy comes from a principle of thermodynamics dealing with energy. It usually refers to the idea that everything in the universe eventually moves from order to disorder, and entropy is the measurement of that change.
The word entropy finds its roots in the Greek entropia, which means "a turning toward" or "transformation." The word was used to describe the measurement of disorder by the German physicist Rudolph Clausius and appeared in English in 1868. A common example of entropy is that of ice melting in water. The resulting change from formed to free, from ordered to disordered increases the entropy.