1734, "to render neutral" (in a chemical sense), from French neutraliser (17c.), from neutral (see neutral (adj.)). Meaning "to counterbalance, render inoperative, invalidate" is by 1795; as an underworld euphemism for "to kill (someone)," by 1987. The intransitive sense "remain neutral" is older (1660s) but is now obsolete. Related: Neutralized; neutralizing.
D. Harper. “Etymology of neutralization.” Online Etymology Dictionary. https://www.etymonline.com/word/neutralization (accessed $(datetime)).
Definitions of neutralization
action intended to keep a country politically neutral or exclude it from a possible war;
the neutralization of Belgium
a chemical reaction in which an acid and a base interact with the formation of a salt; with strong acids and bases the essential reaction is the combination of hydrogen ions with hydroxyl ions to form water;