détente: [20] English originally acquired this word from French in the 17th century as detent, which denotes a catch that regulates the movement of a clock. French détente, which originally signified a device for releasing a crossbow string, came from the past participle of Old French destendre ‘release’, a compound verb formed from the prefix des- ‘apart’ and tendre ‘stretch’ (related to English tension).
But English-speakers, mistakenly associating it with detain [15] (a verb of completely different origin, via Old French detenir from Latin dētinēre ‘keep back’) completely reversed its meaning, applying to a restraining catch rather than a releasing one. French, the language of diplomacy, re-lent détente to English in the first decade of the 20th century in the sense ‘relaxation of international tension’. => tension
