hypertonic (adj.)

word-forming element meaning "over, above, beyond," and often implying "exceedingly, to excess," from Greek hyper (prep. and adv.) "over, beyond, overmuch, above measure," from PIE root *uper "over."

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).