An Etymological Dictionary of Astronomy and Astrophysics

Generally, a measure of the water vapor content of the air. Popularly, it is used synonymously with → relative humidity. → absolute humidity, → dew point, → mixing ratio, → specific humidity.

Etymology (EN): Humidity, from O.Fr. humide, from L. humidus “moist, wet,” variant (by influence of humus “earth”) of umidus, from umere “be moist.”

Etymology (PE): Nam “humidity, moisture,” from Mid.Pers. nam, namb “moisture;” Av. napta- “moist,” nabās-câ- “cloud,” nabah- “sky;” cf. Skt. nábhas- “moisture, cloud, mist;” Gk. nephos “cloud, mass of clouds,” nephele “cloud;” L. nebula “mist,” nimbus “rainstorm, rain cloud;” O.H.G. nebul; Ger. Nebel “fog;” O.E. nifol “dark;” from PIE *nebh- “cloud, vapor, fog, moist, sky.”