E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A strong current or furious tide betwixt island groups.
This lofty promontory is constantly exposed to the current of a strong and furious tide, which, setting in betwixt the Orkney and Zetland islands, and running with force only inferior to that of the Pentland Frith, is called the. Roost of Sumburgh [from the headland].Sir Walter Scott: The Pirate, chap. i.