Pion is also the name of a subatomic particle. See here, toward the bottom. Other subatomic particles are named bosons, fermions, and quarks.

My son and his wife have several cats: Pion (pictured), Boson, Fermion, and Quark. (This Quark is not the bartender on DS-9.) You might not be surprised when I say that his wife is a physics professor.