1821, American English, from shot (n.) in the sense of "lead in small pellets" (1770) + gun (n.). As distinguished from a rifle, which fires bullets. Shotgun wedding is attested by 1903, American English. To ride shotgun is by 1905, from custom of having an armed man beside the driver on the stagecoach in the Old West to ward off trouble.
late 14c., rehersaille, "restatement, repetition of the words of another; account, narration," from rehearse + -al (2), or from Old French rehearsal "a repeating." Sense in theater and music, "act or process of studying by practice or preparatory exercise, a meeting of musical or dramatic performers for practice and study together" is from 1570s. A play being in rehearsal is from 1709. Pre-wedding rehearsal dinner attested by 1953.
"of or pertaining to marriage or the wedding ceremony," late 15c., from French nuptial, or directly from Latin nuptialis "pertaining to marriage," from nuptiae "a wedding," from nupta, fem. past participle of nubere "to marry, get married, wed, take as a husband," which is of uncertain origin. Perhaps it is from a PIE root *sneubh- "to marry, wed" (source also of Old Church Slavonic snubiti "to love, woo," Czech snoubiti "to seek in marriage," Slovak zasnubit "to betroth"). De Vaan finds the old theory that the verb nubere is literally "to cover, veil oneself" (as a bride) semantically attractive but unproven (compare Latin obnubere "to veil, cover the head," from nubes "cloud"). Related: Nuptially.
Nuptial number, a number obscurely described at the beginning of the eighth book of the "Republic" of Plato, and said to preside over the generation of men. The number meant may be 864. [Century Dictionary]