the.com/rain shadow

means The dry zone on the downwind side of a mountain range, where moisture-starved air leaves the land parched because the peaks wrung the rain out before it could cross over.

from A 19th-century term built from plain English parts, not borrowed from Latin or Greek — 'rain' plus 'shadow' used the way a shadow blocks light, here describing how a mountain range blocks moisture. Warm, wet air rises up the windward slope, cools, and dumps its rain and snow there; by the time it crosses the peak and descends the other side, it's wrung dry. The word simply names what you can see on a map: a dry patch sitting in the lee of high ground, as if the mountain cast a shadow made of drought instead of darkness.