In 1932, physics was certainly still fairly easy. Truth be told there were two understood force fields: gravity and EM (the strong field was yet to appear) and several recognized atomic particles: the electron, the proton as well as the neutron. (I am still dubbing them particles just as traditional practices, nevertheless keep in mind that in QFT these are field quanta.) To add in yet another particle or field to this practical, satisfying understanding of nature seemed to be unimaginable. However, there really was this irritating enigma in regard to beta rot.
Pauli’s postulated particle. A clue to the mystery became that the discharged beta rays contain a variety of energies, meaning that some energy must absolutely be going somewhere else. This led Wolfgang Pauli to suggest that in case a second particle is expended from the nucleus at the same instant as the electron, it could easily transport the unaccounted-for energy. He referred to the theoretical particle the “neutron”, however the instant that name was usurped by Rutherford a couple of years down the road, Enrico Fermi relabelled Pauli’s particle the neutrino (Italian for “little neutral one”).
“I admit that my expedient may seem rather improbable from the first, because if neutrons [i.e., neutrinos] existed, they would have been discovered long since. Nothing ventured, nothing gained … We should therefore be seriously discussing every path to salvation.”— W. Pauli (quoted in F. Reines’ Nobel lecture, 1995).