Found lot of use full stuff in that link, but regarding the prefixes only one line(see below) was there and that too didn't explain much, I need to know whether pr stands for Pega Rules or something like that.
Names of standard PegaRULES database tables begin with pr_, pc_, or pi_
I feel there are no PDN articles for same. The purpose of these tables could be explored/understood by the class they map to. As you mentioned pr_operators map to Data-Admin-Operator-ID. Also most of the table names OOTB seems to be self explanatory.