The Free On-line Dictionary of Computing (30 December 2018):

linear argument

    A function argument which is used exactly once by the
   function.

   If the argument is used at most once then it is safe to
   inline the function and replace the single occurrence of the
   formal parameter with the actual argument expression.  If the
   argument was used more than once this transformation would
   duplicate the argument expression, causing it to be evaluated
   more than once.

   If the argument is sure to be used at least once then it is
   safe to evaluate it in advance (see strictness analysis)
   whereas if the argument was not used then this would waste
   work and might prevent the program from terminating.

   (1994-11-03)