The headword, presumably extracted from the first quotation given [on the second, see n. 2 below], is third person plural, imperfect middle, of the verb a)ntana/gw.
[1] Perhaps Diodorus Siculus, according to Adler. Pachynon is at the SE extremity of Sicily; see Barrington Atlas map 47 grid G5 [Pachynum]; cf. epsilon 3524, which again has been attributed to Diodorus.
[2] Not identified by Adler, but (as TLG searching shows) a close approximation of Philostratus, Life of Apollonius of Tyana 4.23 (read a)ntanh/gagon au)to/ for the Suda's a)ntanh/gonto); see on this identification Theodoridis' Photius edition, vol.II p.XCVII. Mt. Oita, in central Greece (Barrington Atlas map 55 grid C3 [Oeta Mons]), was the site of the death of Heracles; here Apollonius calls this to mind when contemplating the tomb of Leonidas and the 300 Spartans at Thermopylai (Barrington Atlas map 55 grid D3).