The Collaborative International Dictionary of English v.0.48:

Insinew \In*sin"ew\, v. t. [imp. & p. p. Insinewed; p. pr. &
   vb. n. Insinewing.]
   To strengthen, as with sinews; to invigorate. [Obs.]
   [1913 Webster]

         All members of our cause, . . .
         That are insinewed to this action.       --Shak.
   [1913 Webster]