The Collaborative International Dictionary of English v.0.48:

Stith \Stith\ (st[i^]th), a. [AS. st[imac][eth].]
   Strong; stiff; rigid. [Obs. or Prov. Eng.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stith \Stith\, n. [Icel. ste[eth]i an anvil, akin to sta[eth]r
   place. See Stead.]
   An anvil; a stithy. [Obs. or Prov. Eng.]
   [1913 Webster]

         He invented also pincers, hammers, iron crows, and the
         anvil, or stith.                         --Holland.
   [1913 Webster]