An Etymological Dictionary of Astronomy and Astrophysics

A substance whose physical state is such that it always occupies the whole of the space in which it is contained.

Etymology (EN): Gas, from Du. gas, probably from Gk. khaos “empty space,” → chaos. The term gas was coined by the Belgian physician Jean-Baptiste van Helmont (1579-1644) to designate aerial spirits.

Etymology (PE): Gâz, loanword from Fr.