DuckCorp Dico

Found one definition

1.                 From The Collaborative International Dictionary of English v.0.48:
                   
   
   
                   
                     
   Tain \Tain\, n. [OE. tein, teyne; cf. Icel. teinn a twig, akin
      to AS. t[=a]n, Goth. tains.]
      Thin tin plate; also, tin foil for mirrors. --Knight.
      [1913 Webster]