Source : Webster's Revised Unabridged Dictionary (1913)

Withernam \With"er*nam\, n. [AS. wi[eth]ern[=a]m; wi[eth]er
   against + n[=a]m a seizure, fr. niman to take.] (Law)
   A second or reciprocal distress of other goods in lieu of
   goods which were taken by a first distress and have been
   eloigned; a taking by way of reprisal; -- chiefly used in the
   expression capias in withernam, which is the name of a writ
   used in connection with the action of replevin (sometimes
   called a writ of reprisal), which issues to a defendant in
   replevin when he has obtained judgment for a return of the
   chattels replevied, and fails to obtain them on the writ of
   return. --Blackstone.