When Adding a Second "PS" at the End of a Letter, It's "PPS", Not "PSS"

When Adding a Second “PS” at the End of a Letter, It's “PPS”, Not “PSS”.

This, of course, is because “PS” stands for “postscript”. This comes from the Latin “post scriptum” (sometimes written “postscriptum”), which translates to “written after”, or more to the point, “what comes after ...