1915, in mechanical descriptions of humidifier systems, agent noun from moisturize.
Entries linking to moisturizer
moisturize v.
"impart moisture to, remove dryness, make slightly damp or wet," 1915 (implied in moisturizing), in reference to a commercial egg incubator, from moisture + -ize. By 1953 in reference to creams and lotions for the skin. Related: Moisturized; moisturization.