Etymology of "shark"

I found Etymonline's entry on the word shark unusually inconclusive. Not only is the origin of the word uncertain, it is also not clear if shark was first applied to a dishonest person or to the sea creature.

It also had no mention of this positive connotation from NOAD:

2 an expert in a specified field : a pool shark.

Can any etymology sharks out there supply some of these missing links?

Carcharus is Latin for dogfish, (deriving from Greek carcharos jagged: Carcharodon, the scientific name for the Great White family, means 'sharp tooth'), so could be the origin. Also possible are Austrian German Schirk, sturgeon, or dialect French cherquier to seek, as well as German schurke scoundrel or Mayan Xoc. Finding all these in 10 minutes suggests to me that the true origin (whatever it is) is buried in a pile of plausible falsehoods. (I evolved one of my own: could it be a mishearing of 'shagreen' [a leather made from skins of rays or sharks] as 'sharkskin'? Sadly, shagreen, from chagrin untanned leather, seems to be younger than shark.) It is suggestive, though, that the word came into English about the time that British sailors were first sailing to the Caribbean and South Atlantic, where sea sharks are found, while land sharks (lawyers, salvagemen, wreckers, etc) had been around for centuries.

"The Xoc, the Sharke, and the Sea Dogs: An Historical Encounter". 16Century from a Mayan word apparently.

But since sharks are fairly common in the North Atlantic and Mediterranean - I can't believe there wasn't an older term.

The OED gives the following history:

The word seems to have been introduced by the sailors of Captain (afterwards Sir John) Hawkins's expedition, who brought home a specimen which was exhibited in London in 1569. The source from which they obtained the word has not been ascertained. Cf. Ger. dial. (Austrian) schirk sturgeon

It disparages the idea that the noun came from the verb:

The conjecture of Skeat that the name of the fish is derived from shark v.1 is untenable; the earliest example of the vb. is c 1596, and the passage alludes to the fish

Just heard that Shark in Arabic is called a Kirsh - in arabic it's the letters Q-R-Sh - reversed would give us Sh-R-Q - then came here to see if I was wrong. Just a hypothesis but maybe the origin is arabic