late 14c., of grammatical gender, "neither masculine nor feminine," 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). Probably a loan-translation of Greek oudeteros "neither, neuter." In 16c., it had the sense of "taking neither side, neutral."
1903, from neuter (adj.). Originally in reference to pet cats. Related: Neutered; neutering.