impregnable

Etymology 1

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.

adj

1. (military) Of a fortress or other fortified place: able to withstand all attacks; impenetrable, inconquerable, unvanquishable.
2. (figurative) Too strong to be defeated or overcome; invincible.
   And with Bolton suffering a wretched run of five straight home defeats – their worst run in 109 years – Chelsea fans would have been forgiven for expecting a comfortable win. But surely they did not anticipate the ease with which their team raced into an almost impregnable half-time lead. 2 October 2011, Jonathan Jurejko, “Bolton 1 – 5 Chelsea”, in BBC Sport, archived from the original on 2021-12-31

Etymology 2

PIE word *h₁én From impregnate (verb) + -able (suffix meaning ‘able or fit to be done’ forming adjectives). Impregnate is either derived from impregnate (“pregnant”, adjective), or from its etymon Medieval Latin or Late Latin impraegnātus (“made pregnant”), past participle of impraegnō (“to make pregnant”), from Latin im- (a variant of in- (prefix meaning ‘in, inside, within’) + praegnāre (“pregnant”) (from praegnāns, a variant of praegnās (“pregnant”), from prae- (prefix meaning ‘before; in front’) + *gnāscor (archaic), nāscor (“to be born; to grow, spring forth; to arise, proceed”) (ultimately from Proto-Indo-European *ǵenh₁- (“to beget; to give birth; to produce”))).

adj

1. Capable of being impregnated; impregnatable.
   The reproductive strategies of troop members, especially those of impregnable females, are suggested to influence patterns of range use. 1979 November, Dennis R. Rasmussen, “Correlates of Patterns of Range Use of a Troop of Yellow Baboons (Papio cynocephalus). I. Sleeping Sites, Impregnable Females, Births, and Male Emigrations and Immigrations.”, in Animal Behaviour, volume 27, number 4, New York, N.Y.: Elsevier Science Pub. Co., →DOI, →ISSN, →OCLC, abstract, page 1098