The story
From sterile + neutrino, from being a neutrino which is sterile, being noninteractive through the four forces of the Standard Model.
Etymology from Wiktionary, CC BY-SA 4.0.
sterile neutrino
Today it means: A type of neutrino (and potentially dark matter), that may be supermassive, which has right-handed chirality, and only interacts with other particles by means of gravity. Full definition →