S.Baring-Gould

After they had sinned, they were given bodies of flesh; for an angel who spends seven days on earth becomes opaque and substantial.

From these angels descend the sons of the giants and the Anakim, and from their seed also spring the devils.

And the book Zeenaureena, in the Parascha Chykkath, says that Og sprang from this connection, and that Sammael, the angel, was the parent of Og, but that Sihon was the son of the same angel who deceived the wife of Ham when she was about to enter the ark.1