The PM9J (not PMJ9) is Jock's long shootin' short nosed PM9, which has been renamed in honor of the many thousands of rounds he has fired through it. One might say the pistol is damn near enshrined (or was that encrusted? no matter....).
I coined the term.
However, one must account for the famed and legendary typing skills of our beloved Jocko. Therefore, when Jocko types: "Thsi is my PMJ9 an I shoot the foker liek I sotle it", we end up being more endeared to his earthly presence.