"Withernam" is a word in LAW AND LEGAL, ENGLISH

In practice. A taking by way of reprisal; a taking or a reprisal of other goods, in lieu of those that were formerly taken and eloigned or withholden

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.