late 15c., "a casting down" (of the evil angels from heaven), also, in alchemy "separation of a solid substance from a solution," from Middle French precipitation (15c.) and directly from Latin praecipitationem (nominative praecipitatio) "act or fact of falling headlong, haste," noun of action from past participle stem of praecipitare "fall, be hasty," from praeceps "steep" (see precipice). Meaning "sudden haste" is c.1500. Meaning "act of falling from a height" is attested from 1610s. Meteorological sense of "rain, snow, dew, etc." is from 1670s.
precipitation pre·cip·i·ta·tion (prĭ-sĭp'ĭ-tā'shən)
The process of separating a substance from a solution as a solid.