c.1500, "without speech, silent, not speaking," from Latin silentem (nominative silens) "still, calm, quiet," present participle of silere "be quiet or still" (see silence (n.)). Meaning "free from noise or sound" is from 1580s.
Of letters, c.1600; of films, 1914. In the looser sense "of few words," from 1840. Phrase strong, silent (type) is attested from 1905. Silent majority in the political sense of "mass of people whose moderate views are not publicly expressed and thus overlooked" is first attested 1955 in a British context and was used by John F. Kennedy but is most associated in U.S. with the rhetoric of the Nixon administration (1969-74).
In Victorian use, the phrase meant "the dead" (1874; cf. Roman use of the noun plural of "silent" to mean "the dead"). Silence is golden (1831) is Carlyle's translation ["Sartor Resartus"] of part of the "Swiss Inscription" Sprechen ist silbern, Schweigen ist golden.