E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Old Harry. Old Scratch. To harry (Saxon) is to tear in pieces, whence our harrow. There is an ancient pamphlet entitled The Harrowing of Hell. I do not think it is a corruption of Old Hairy, although the Hebrew Seirim (hairy ones) is translated devils in Lev. xvii. 7, and no doubt alludes to the he-goat, an object of worship with the Egyptians. Moses says the children of Israel are no longer to sacrifice to devils (seirim), as they did in Egypt. There is a Scandinavian Hari = Baal or Bel.