The term "white noise" is a modern scientific metaphor, first used in the early 20th century. It directly analogizes from the concept of "white light" in physics, which is light containing all visible wavelengths in equal intensity. By transferring this property to sound, "white noise" describes a random signal with equal intensity across all audible frequencies, producing a steady hiss. The "white" thus evolved from a visual descriptor of brightness and purity to an abstract technical label for statistical uniformity and comprehensiveness within a signal spectrum. This compound elegantly bridges optics and acoustics, using a common color term to conceptualize a complex auditory phenomenon.

Structure: white + noise - white: From Old English hwīt, meaning "bright, radiant, clear, fair." In this compound, it functions as an adjective modifying the type of "noise," drawing an analogy to "white light." - noise: From Old French noise, meaning "din, disturbance, quarrel," of uncertain origin, possibly from Latin nausea (disgust, seasickness). In this compound, it functions as the head noun, meaning "sound."