- tonic (adj.)
- 1649, "relating to or characterized by muscular tension," from Gk. tonikos "of stretching," from tonos "a stretching" (see tenet). The meaning "maintaining the healthy firmness of tissues" is recorded from 1684, first extended 1756 to "having the property of restoring to health." The noun meaning "a tonic medicine" is attested from 1799. The musical sense is first attested 1760, from tone (q.v.).