The English and French word "air" is derived from the Latin aer, which comes from the Greek alpha eta rho. In contrast, the German word "Luft" is a common Proto-Germanic word; in Old English "lift" and "lyft". The word Luft (also Danish, Swedish and Norwegian) is associated with brightness; the German Licht (light), an air (in an atmospheric sense) without fog or clouds. Air and water were originally "elements" in ancient Greek and were transmutable; they represented two kinds of the "layer of mist" (atmosphere). Dark or thick air was mist or cloud, hiding the gods (who lived in the upper air or sky; the aether). Different terms are presented that describe fog and clouds in connection with the history of the process of understanding. Finally, the word Luft (air) as a term for gaseous chemical compounds ("kinds of gases") is discussed. In addition to the German, all terms are given in Greek, Latin, English and French.
