We detached this subthread from https://news.ycombinator.com/item?id=12834661 and marked it off-topic.

When an acronym/initialism is ambiguous, you can repeat the last word to make what you're saying unambiguous. ATM machine is easily distinguished from ATM mode. Similarly, you could say a LEO orbit to distinguish from a LEO officer.

No matter what, it's not nearly as bad as "The Los Angeles Angels" :-)

The original PAM RFC defines PAM as Pluggable Authentication Modules (plural – it’s the name of the framework and not one of its components), so it’s fine and more natural to say “PAM module”.

Also known as PNS Syndrome (PIN Number Syndrome (Personal Identification Number Number Syndrome Syndrome)).

Except PAM stands for "Pluggable Authentication Modules" (as in "PAM Library") - plural.

You then write a module for the PAM library, so it makes the most sense to call it a "PAM Module", even if there is some redundancy in the acronym.

Why does it matter?

English isn't a programming language; it's OK if some of the things expressed commonly by natural language speakers aren't perfectly regular or logical, as long as everyone understands them. In this case, "PAM module" is totally understandable, and less ambiguous than just "PAM".

It's not as if every 3 letter acronym has one canonical definition. Googling a 3 letter acronym is almost impossible without adding at least one of the full words. The "ATM machine" pattern seems to me to be the most concise way of removing that ambiguity. It's interesting how language evolves.

Heavens to Betsy! You got me. But I do hope someone writes a module for the macos PAM system implementation.

Can you elaborate? I'm not sure to understand the "ATM machine thing" and the "feels wrong on the lips".