Whenever I talk about maths here, Americans ask why Brits use the plural of math. I have an utterly unproven theory suggesting that it’s not a plural at all.
Years ago, I heard a story that explained why Hampshire is abbreviated to Hants on British letters. In 1086 when the Domesday Book was penned, Hampshire was called Hantescire. As people began to write letters and found the practice too labour-intensive, they chose to abbreviate their words. To avoid confusion, they put a little sign at the end of those words to show that they’d been abbreviated. The little sign looked like this: ～
“Hantescire” was abbreviated to “Hant～”.
Over time, the ～ rolled over, tipped sideways, and slid down, turning “Hant～” into “Hants”.
Maybe the same thing happened to mathematics.