neutrino (n.)

late 14c., neutre, in grammar, of nouns, pronouns, etc., "neither masculine nor feminine in gender," also of verbs, "having middle or reflexive meaning, neither active nor passive," from Latin neuter "of the neuter gender," literally "neither one nor the other," from ne- "not, no" (from PIE root *ne- "not") + uter "either (of two)" (see whether). The Latin word is probably a loan-translation of Greek oudeteros "neither, neuter." From 1520s it also had the sense of "taking neither side" which now generally goes with neutral (adj.).

As a noun from mid-15c., "the neuter gender;" by 1797 of certain animals (among bees, ants, etc.) that are of neither sex and incapable of generation.