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

memory protection

    A system to prevent one process
   corrupting the memory (or other resources) of any other,
   including the operating system.  Memory protection usually
   relies on a combination of hardware (a memory management
   unit) and software to allocate memory to processes and handle
   exceptions.

   The effectiveness of memory protection varies from one
   operating system to another.  In most versions of Unix it is
   almost impossible to corrupt another process' memory, except
   in some archaic implementations and Lunix (not Linux!).
   Under Microsoft Windows (version?  hardware?) any 16 bit
   application(?) can circumvent the memory protection, often
   leading to one or more GPFs.  Currently (April 1996) neither
   Microsoft Windows 3.1, Windows 95, nor Mac OS offer
   memory protection.  Windows NT has it, and Mac OS System 8
   will offer a form of memory protection.

   [MS DOS EMM386 relevant?]

   (1996-09-10)