I.a prop, support, used to keep ships upright when ashore, Il.: metaph. of men, ἕρμα πόληος prop or stay of the city, Lat. columen, Hom.; μελαινέων ἕρμ᾽ ὀδυνάων, of a sharp arrow, the foundation, i. e. the cause, of pangs, Il.
II.a sunken rock, reef, on which a vessel may strike, Hdt., Aesch., etc.
III.a mound, cairn, barrow, Soph.
IV.that which keeps a ship steady, ballast, Plut.
deriv. uncertain