Mathematics are plural because it's a group of several disciplines, arithmetic and geometry today (music and astronomy used to be two other math branches in the past). It's actually an adjective that became a noun, so these four were the disciplines mathématiques, becoming simply les mathématiques later on.

At least that's why it's plural in French. I wouldn't be surprised if the English term is plural simply because it comes from French.

There are shortened forms of singular nouns that end in -s, which also end in -s. Some forms are more common in some cultures/places - "stat" vs "stats" for "statistics" comes to mind.

Yes, I'm also very peeved by "maths". And a million other things. Calling Universities "Uni". Horned-Rim glasses. A whole slew of grammatical oddities.

I guess that's why I ended up on this site.

You know that “math” is just the abbreviated form of “mathematics” right?

"mathematics" may end in "s", but that doesn't make it plural. We say "Mathematics is a science" not "Mathematics are sciences" (replace with "art/arts" if you don't belive it's a science). We also say "mathematics is a growing field", not "mathematics are growing fields". Because it's singular, the fact that it ends in "s" doesn't naturally require shortened forms of it to carry the last letter at the end. I get that in the UK people say "maths", but let's not make this out to be like one side is correct and the other is not because mathematics ends in "s". Particularly as "math" was first coined in the U.K. (much of contemporary U.S. English is an older form of contemporary British English).

I didn't say it's plural, I said it's the abbreviated form. Math and maths are both abbreviations of mathematics.

You changed the post I was responding to, which was something to the effect of "don't you know mathematics ends with 's'"?

No, I did not.