Note 23 — Chapter I · INTRODUCTORY.
Reading edition
This is probably the modern form of ἐμπόδευμα, ‘entanglement.’ The change of initial ε to α is not rare in dialect, cf. ἄρμος for ἔρμος (= ἔρημος) ‘miserable’; and υ, with sound of English v, is regularly lost before μ.