Yeah, it sounds kind of weird, but you are right of course. We got an example of that in "atoms": originally they were supposed to mean "indivisible minimal components", and for a long time the 4 elements were supposed to be types of atoms... until we discovered that atoms can be divided into even smaller particles (electrons, protons, neutrons), and those particles in turn into even smaller ones yet (quarks), then we had to come with the word "quanta" to mean the new "indivisible minimal component" since "atom" got entrenched to mean "a clump with this number of protons" which nonetheless could vary in the number of neutrons (isotopes) and electrons (ions).

On the bright side, the "quanta" are now a moving target, applicable to "whatever we don't know how to divide any further"... but we might learn how to in the future.

the circle

IMHO, it is likely going to get explained at some point in the future why the circle is a circle, and why pi has the value we see, for us. It might take some radical explanation of the nature of space-time, which will "naturally" give raise to the value of pi, and at the same time describe spaces where it would take different values.