Why is the ninth month called September?
early 13c., "loud outcry, clamor, shouting," from Old French noise "din, disturbance, uproar, brawl" (11c., in modern French only in phrase chercher noise "to pick a quarrel"), also "rumor, report, news," apparently from Latin nausea "disgust, annoyance, discomfort," literally "seasickness" (see nausea).
Another theory traces the Old French word to Latin noxia "hurting, injury, damage." OED considers that "the sense of the word is against both suggestions," but nausea could have developed a sense in Vulgar Latin of "unpleasant situation, noise, quarrel" (cf. Old Provençal nauza "noise, quarrel"). Meaning "loud or unpleasant sound" is from c.1300. Replaced native gedyn (see din).
late 14c., "to praise; to talk loudly about," from noise (n.). Related: Noised; noising.
Any part of a signal that is not the true or original signal but is introduced by the communication mechanism.
A common example would be an electrical signal travelling down a wire to which noise is added by inductive and capacitive coupling with other nearby signals (this kind of noise is known as "crosstalk").
A less obvious form of noise is quantisation noise, such as the error between the true colour of a point in a scene in the real world and its representation as a pixel in a digital image.