late 15c., "composed of contrasting elements which, in proper proportion, neutralize each other," from Middle French neutral, from Latin neutralis "of neuter gender," from neuter (see neuter (adj.)). Chemistry sense is from 1660s. Sense of "not taking sides in a fight" (1540s) probably is from a similar meaning in Medieval Latin. Of colors, from 1821. Neutral corner is from boxing (1908).