PPN

 PPN (pip'in) [DEC terminology, short for Project-Programmer Number]
       n. 1. A combination `project' (directory name) and programmer name,
       used to identify a specific directory belonging to that user. For
       instance, "FOO,BAR" would be the FOO directory for user BAR.
       Since the name is restricted to three letters, the programmer name is
       usually the person's initials, though sometimes it is a nickname or
       other special sequence. (Standard DEC setup is to have two octal
       numbers instead of characters; hence the original acronym.) 2. Often
       used loosely to refer to the programmer name alone. "I want to
       send you some mail; what's your ppn?" Usage: not used at MIT,
       since ITS does not use ppn's. The equivalent terms would be UNAME and
       SNAME, depending on context, but these are not used except in their
       technical senses.