Re: I raise you a fourth family...
"I think it was Fermi who came up with that to explain mysterious missing momentum in subnuclear physics, apparently going to a particle that did not show up on any photographic plates"
It was actually Pauli, and the problem was boring old beta decay. Whereas alpha particles for a given disintegration all had more or less the same energy (with minor caveats), the electrons emitted in beta decay were all over the place. The electron energies and the nuclear recoil did not add up to a constant value and, even worse, were not in a straight line. Bohr even considered abandoning strict conservation of energy, which would have been exciting. Pauli posited that a neutral particle was being emitted and called it a neutron. Unfortunately Chadwick discovered the other, big neutron around the same time. Instead of fighting it out with particle accelerators at dawn, an Italian physicist named Amaldi suggested calling Pauli's neutron by a diminutive - neutrino - and Fermi adopted this, with Pauli agreeing. So Fermi was only very peripherally involved, like Storey who named the electron despite not being a major figure in electrical theory.
What is interesting (to me at least) about neutrinos is that they are so common, carry so much energy as a whole, turn up in such an apparently bread and butter phenomenon, and yet are so hard to detect and so weird. They're an argument that dark matter or dark energy may be hiding in plain sight, we just don't know where to look or know what we're looking for.