conditioner n.

late 15c., "to make conditions, stipulate," from condition (n.). Meaning "subject to something as a condition" is from 1520s; sense of "form a prerequisite of" is from 1868. Meaning "to bring to a desired condition" is from 1844; psychological sense of "teach or accustom (a person or animal) to certain habits or responses" is from 1909. Related: Conditioned; conditioning.

from air (n.1) + conditioner. Along with air-conditioning first attested 1909, originally in reference to an industrial process in textile manufacturing. The word conditioning was applied to the determination of the moisture content of textiles, control of which was essential to spin fine cotton yarns. The original purpose of air-conditioning was to purify air and regulate moisture.

In 1906 Stuart W. Cramer of Charlotte, N.C., and Willis H. Carrier of Buffalo, N.Y., independently devised methods of using a fine spray of water to cool air. Self-contained air-conditioning units, complete with refrigeration equipment, were widely used to cool air in U.S. stores, restaurants, etc. from the 1930s. An earlier name for such a device (using ice and fans) was air cooler (1875).