E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A swindler, a pilferer; one who snaps up things like a shark, which eats almost anything, and seems to care little whether its food is alive or dead, fish, flesh, or human bodies.
These thieves doe rob us with our owne good will,
And have Dame Natures warrant for it still;
Sometimes these sharks doe worke each others wrack,
The ravening belly often robs the backe.
Taylors Workes, ii. 117.
The shark flies the feather. This is a sailors proverb founded on observation. Though a shark is so voracious that it will swallow without distinction everything that drops from a ship into the sea, such as cordage, cloth, pitch, wood, and even knives, yet it will never touch a pilot-fish (q.v.) or a fowl, either alive or dead. It avoids sea-gulls, sea-mews, petrels, and every feathered thing. (St. Pierre: Studies, i.)