Against ‘Folk Scholarship’

Acronym Ending Letters

In Hebrew, we find regular letters –

אבג…כלמנ

And then there are Ending Letters, like these –

ךםן…ףץ

When writing Hebrew acronyms which employ last letters like Mem, Chaf, Nun, etc., which form should the final letter take?

Some acronyms simply use Middle Letters –

ה”מ, ש”מ, עאכו”כ, נפק”מ

Many others have Ending Letters, like these –

תנ”ך, רמב”ן, עכו”ם, רמב”ם

So, what is the rule? When is the last letter an “Ending Letter”, and when is it not?

Of course, one could just follow one’s “intuition” (as in: “When does one add the connective ‘Es’?”). This ‘folk scholarship’ seems to substitute for formal knowledge of many literary Torah fields, unfortunately.

As I see it, there are two options:

1. Nouns or concepts get finalized letters, phrases, however common, do not.
2. The more commonly used acronyms get finalized letters, while all others do not.

I do not own a huge list of acronyms to verify either theory.

I may have a way to gain better clarity. Perhaps one of our readers can check out Arabic or Greek. These languages, too, possess final forms for some letters in their alphabet. What is their standard operating procedure for initialisms/acronyms?