The headword is a feminine noun (omicron 591), here in the accusative plural; see generally LSJ and Hesychius s.v. o(rka/nh. It is taken to be extracted from Euripides, Bacchae 611 (web address 1), where Dionysus asks how the chorus-leader felt when he (Dionysus) was being cast into what seemed to be Pentheus' prison chambers.
[1] The headword is identically glossed in the Synagoge, Photius' Lexicon (omicron482 Theodoridis), and Lexica Segueriana 320.21 (though in this last the headword has its accent on the ultima, o(rkana/s. Compare also Hesychius omicron1228 (nominative singular).