or Tars. Sailors, more frequently called Jack Tars. Tarpaulins are tarred cloths used commonly on board ship to keep articles from the sea-spray, etc.
The more correct spelling is tar-palling, from pall, Latin pallium, a cloak or cloth.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Tarpaulins from Fact Monster: