It’s not jargon at all, is it? It’s just literally the proper name for the specific payment network. I thought jargon is industry-specific slang terms for concepts that could otherwise be described with less industry-specific terms. There is no simpler or clearer way I’m aware of to refer specifically to ACH.

As for it being common, if you work as a developer on any web products that accept or send significant payments in the US, you’ve almost certainly heard of ACH. If you haven’t, then this article probably won’t be of any interest or use to you even if it had an extensive introduction about what ACH is.