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

copying garbage collection

   A garbage collection method where memory is divided into two
   equal halves, known as the "from space" and "to space".
   Garbage collection copies active cells from the from space to
   the to space and leaves behind an invisible pointer (an
   "indirection") from the old position to the new copy.  Once
   all active cells have been copied in one direction, the spaces
   are swapped and the process repeated in the opposite
   direction.