borrowed from New Latin gynoeceum, from gyn-gyn- + Greek oîkos "house, home" + -eum, for Greek -eion, noun suffix — more at vicinity
The history of this word is less straightforward than one might expect. It was introduced by the German botanist Johannes Röper (1801-85) in "Observationes aliquot in florum inflorescentiarumque naturam," Linnaea, Ein Journal für die Botanik, 1. Band , pp. 433-570. Röper uses the spelling gynoeceum (as in the above etymology) and gives as its derivation in a footnote "ex γυνη et οἰκος" (sic, without accents or glosses). For its correlative androecium Röper has in a footnote "ex ἀνηρ et οἰκος." The initial difficulty is that his gynoeceum hints at an actual Latin and Greek word: classical Latin gynaecēum, gynaecīum "women's quarters in a Greek house," borrowed from Greek gynaikeía, with the same sense. (A neuter noun is not recorded in Liddell and Scott or the Cambridge Greek Lexicon.) The latter word, however, is simply a nominal derivative of the adjective gynaikeîos "of women," derived from gynaik-, gynḗ "woman," and has no connection with oîkos "house" or oikía "dwelling, household." Subsequently both other authors and Röper himself (in De floribus et affinitatibus balsaminearum, Basel, 1830) used the spelling gynaeceum, bringing it closer to Greek gynaikeía, but muddying Röper's own etymology. As another difficulty gyn- and gyno- are rarely used in Greek as bases in compounding, the overwhelming preference being given to gynaiko- (see gyno- and gyneco-); the more regular compounding of gynḗ and oîkos would hence be the sesquipedalian gynaecoeceum, which has apparently never been used. The current predominant variant gynoecium, with -i- replacing -e- as a representative of Greek -ei-, was apparently first used by the English botanist George Bentham in Labiatarum genera et species (London, 1832-36). Dictionaries have tended to treat gynoecium as a mangling by folk etymology of gynaecēum, but, in an article scornful of the attempts by classicists and lexicographers to adjust botanical nomenclature, the botanist Arthur Harry Church insisted on the correctness of gynoecium ("Androecium and Gynaecium," Journal of Botany, British and Foreign, vol. 57 , pp. 220-23).