impregnable

Origin

From Late Middle English imprenable, impregnable (“impossible to capture, impregnable”), from Old French imprenable (modern French imprenable (“impregnable”)), from im- (a variant of in- (prefix meaning ‘not’) + prenable (“(military) of a building, position, etc.: takable”) (from prendre (“to take”) + -able (suffix meaning ‘creating an effect or influence’)). Prendre is derived from Latin prēndere, present active infinitive of prēndō, a variant of prehendō (“to catch, lay hold of; to grasp; to grab, snatch; to seize, take”), ultimately from Proto-Indo-European *gʰed- (“to find; to hold; to seize, take”). The intrusive g in the English word was modelled after words like deign and reign.