V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

PLM
       Programming Language for Microcomputers


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

PL/M

   Programming Language/Microcomputers.  MAA (later Digital
   Research) for Intel, 1972.  A very low level language
   incorporating ideas from PL/I, ALGOL and XPL.  Integrated
   macro processor.  Originally the implementation language for
   CP/M.  "PL/M-80 Programming Manual", Doc 98-268B, Intel 1976.
   "A Guide to PL/M Programming for Microcomputer Applications",
   D. McCracken, A-W 1978.  Versions: PL/M-80, PL/M-86, PL/M-286.