Emily Dickinson Lexicon

GAS, n. [Sax. gast, G. geist, D. geest, spirit, ghost. The primary sense of air, wind, spirit, is to flow, to rush. Hence this word may be allied to Ir. gaisim, to flow; gasaim, to shoot forth, to gush; gast, a blast of wind. It may also be allied to yeast, – which see.]

In chimistry, a permanently elastic aeriform fluid, or a substance reduced to the state of an aeriform fluid by its permanent combination with caloric. Gases are invisible except when colored, which happens in two or three instances.