古英語のmist(霧)、mist(霧)、moist(湿気)から。原語ゲルマン語 *mikhstaz、おそらくPIE *meus(湿気)、wet(湿った)から。
Sometimes distinguished from fog, either as being less opaque or as consisting of drops large enough to have a perceptible downward motion. [OED]Also in Old English in sense of "dimness of the eyes, either by illness or tears," and in figurative sense of "things that obscure mental vision."