Yours, Etc.: Origins and Uses of 8 Sign-Offs
Old English scur "a short fall of rain, storm, tempest; fall of missiles or blows; struggle, commotion; breeze," from West Germanic *skuraz (cf. Old Norse skur, Old Saxon and Old Frisian scur "fit of illness;" Old High German scur, German Schauer "shower, downpour;" Gothic skura, in skura windis "windstorm"), from PIE root *kew-(e)ro- "north, north wind" (cf. Latin caurus "northwest wind;" Old Church Slavonic severu "north, north wind;" Lithuanian šiaurus "raging, stormy," šiaurys "north wind," šiaure "north").
Of blood, tears, etc., from c.1400. Of meteors from 1835. Sense of "bath in which water is poured from above" first recorded 1851 (short for shower-bath, itself attested from 1803). Meaning "large number of gifts bestowed on a bride" (1904, American English colloquial) later was extended to the party at which it happens (1926). Shower curtain attested from 1914.
"one who shows," Old English sceawere "spectator, watchtower, mirror," agent noun; see show (v.).
1570s, "come down in showers;" 1580s, "to discharge a shower," from shower (n.1). Intransitive sense from 1930. Related: Showered; showering.