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

secondary cache
L2 cache
level 2 cache
level two cache
second level cache

    (Or "second level cache", "level two
   cache", "L2 cache") A larger, slower cache between the
   primary cache and main memory.  Whereas the primary cache
   is often on the same integrated circuit as the central
   processing unit (CPU), a secondary cache is usually external.

   (1997-06-25)