1640s, "relating to or characterized by muscular tension," from Greek tonikos "of stretching," from tonos "a stretching," from PIE root *ten- "to stretch." The meaning "maintaining the healthy firmness of tissues" is recorded from 1680s, first extended 1756 to "having the property of restoring to health." Related: Tonical (1580s).
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Definitions of hypertonic
(of living tissue) in a state of abnormally high tension;
hypertonic muscle tissue
(of a solution) having a higher osmotic pressure than a comparison solution;