Yours, Etc.: Origins and Uses of 8 Sign-Offs
1807 (Elizabethean); Coleridge (1817) has Elizabethian, and Carlyle (1840) finally attains the modern form. "Belonging to the period of Queen Elizabeth I" (1558-1603). The noun is first attested 1881. See Elizabeth.
John Knox, one of the exiles for religion in Switzerland, publiſhed his "Firſt Blaſt of the Trumpet againſt the Government of Women," in this reign [of Elizabeth]. It was lucky for him that he was out of the queen's reach when he ſounded the trumpet. [The Rev. Mr. James Granger, "A Biographical History of England," 1769]