Something I always wondered about.
Being a little on the older side, I do remember an A battery, which according to my limited memory, morphed into the AA. I didn't see an AAA until maybe 20 years ago.
Another battery oddity is that the + side of abattery is actually the negative side (where the electrons exit). This is because with the invention of galvanic cells circa 1850, the scientists thought the positive charges moved.
We should change it to be more technically correct, but . . . .