constraint (n.)

late 14c., constreinte, "distress, oppression," a sense now obsolete, from Old French constreinte "binding, constraint, compulsion" (Modern French contrainte), fem. noun from constreint, past participle of constreindre, from Vulgar Latin *constrinctus, from Latin constrictus, past participle of constringere "to bind together, tie tightly, fetter, shackle, chain," from assimilated form of com "with, together" (see con-) + stringere "to draw tight" (see strain (v.)).

Meaning "coercion, compulsion, irresistible force or its effect to restrict or compel" is from 1530s. Especially "repression of emotion or of the expression of one's thoughts or feelings" (1706).