

There are some public numbers on how many occurrences are found each year on the major platforms.
IIRC, Facebook deals with around 75 million reports per year. Twitter, Reddit, and others were around 20 million reports per year.
I don’t know how many are dealt with on Mastodon or Lemmy (or how you’d even get reliable numbers for that), but something tells me it’s a lot less than the bigger platforms these days.
As others have mentioned, it refers to the gear shift. But it actually has a meaningful origin - many years ago, the gear order was not agreed upon. Many cars had a gear shift that was PNDLR (which I’ve heard pronounced “pendler”), where reverse was at the end. At the time, it was useful to tell the difference between a PRNDL and a PNDLR shift.
Of course that was all before 1971, when PRNDL was mandated by the US government.