I was going over intervals with a student today, and, as frequently happens, he thought the next interval after "major seventh" was "perfect eighth." He was of course embarrassed that he didn't realize it was also called an octave, since there's a key on the saxophone with that name...
KID: Oh, right...oct- as in octagon.
ME: Yup, and octopus. And the eighth month of the year used to be October, just like SEPT-ember was the seventh month, and November and December were the ninth and tenth.
KID: But wait--that's only ten months!
ME: Right...until the Romans got hold of the calendar and added two months named after their most famous Caesars.
KID: (thinks for a second) So what would that be...May?