An Etymological Dictionary of Astronomy and Astrophysics

1. Anything likened to a window in appearance or function.
   
2. In particular, the wavelength region in the electromagnetic spectrum that is relatively unaffected by atmospheric absorption. → atmospheric windows; → infrared window; → optical window; → radio window.

Etymology (EN): Window literally “wind eye,” from O.N. vindauga, from vindr, → wind, + auga,
→ eye.

Etymology (PE): Rowzané, from rowzan “window, aperture;” Mid.Pers. rocânak “window,” rôšn “light; bright, luminous,” from Av. raocana- “bright, shining, radiant,” raocah- “light, luminous; daylight,” related to Mod.Pers. ruz “day,” from Mid.Pers. rôc, O.Pers. raucah-; akin to Skt. rocaná- “bright, shining,” roka- “brightness, light;” Gk. leukos “white, clear;” L. lux “light” (also lumen, luna); PIE base *leuk- “light, brightness.” The Persian words rowšan “bright, clear,” foruq “light,” and afruxtan “to light, kindle” also belong to this family, as well as the E. light, Ger. Licht, and Fr. lumière; forusorx→ infrarouge.