The Collaborative International Dictionary of English v.0.48:

Corporal \Cor"po*ral\ (k[^o]r"p[-o]*ral), Corporale
\Cor`po*ra"le\ (-r?"l?), n. [LL. corporale: cf. F. corporal. See
   Corporal,a.]
   A fine linen cloth, on which the sacred elements are
   consecrated in the eucharist, or with which they are covered;
   a communion cloth.
   [1913 Webster]

   Corporal oath, a solemn oath; -- so called from the fact
      that it was the ancient usage for the party taking it to
      touch the corporal, or cloth that covered the consecrated
      elements.
      [1913 Webster]