Etymology
First use appears c. 1842. See cite below.
Adjective
tough as teak (not comparable)
- (simile) Very tough.
1842, H.H. Chambers (publisher), The New Zealand Journal, Volume 3, page 282:We could not find that she had sustained any material damage, for thanks to the Hindostane builder, the old Brougham is as tough as teak and nails can make her.
1999 August 25, Dr Who, “Most Under Rated Players - This Decade”, in aus.sport.rugby-league (Usenet):Big Salvo was up there with the greatest front rowers of the 90's. Like O'Doherty he had it all. He was as tough as teak, made the hard yards, was a punishing defender, and had amazing ball skills for a man his size. Injury and suspension unfortunately dampened his career, he was somewhat inexplicably dropped as the incumbent test prop after 91. He along with Geyer, Bella, Meninga, etc slaughtered the Kiwi's in that series.
2000, James Hadley Chase, Knock, Knock! Who's There?, page 4:Sammy knew Johnny was as tough as teak and he carried a punch like a sledgehammer blow. Sammy had never forgotten how Johnny had once handled a punk who had tried to pick a quarrel.
2003 October 11, Helen Cushion, “Uncut Magazine Uk November issue”, in alt.music.zevon (Usenet):"beneath their Golden State polish these records are as tough as teak, with a swagger imparted by as good a phrasemaker as ever made rock and roll records."