An Etymological Dictionary of Astronomy and Astrophysics

1. The comparative darkness caused by the interception or screening of rays of light from an object, place, or area.
   

2. A place or an area of comparative darkness, as one sheltered from the sun (Dictionary.com). See also → shadow.

Etymology (EN): M.E. schade; O.E. scead “partial darkness; shelter,” → shadow.

Etymology (PE): Sivân, from Kurd. sayvân “shadow, shade,” variants si, sâ, sâyé, → shadow.