The word derives figuratively from the French word chaperon (originally from the Late Latin cappa, meaning “cape”) which referred to a hood that was worn by individuals generally. A chaperone was part of the costume of the Knights of the Garter when they were in full dress and, probably, since the Knights were court attendants, the word chaperon changed to mean escort. An alternative explanation comes from the sport of falconry, where the word meant the hood placed over the head of a bird of prey to stop its desire to fly.
According to the Oxford English Dictionary the noun (in its figurative sense of escort of females) is attested from 1721, and the verb ‘to chaperon’ from 1811.
Although the supervision of vulnerable females in public spaces may be common in many cultures, the specific word chaperon began to be used in the eighteenth century to denote a particular social institution, namely, a woman who would accompany a young unmarried woman in public, and especially where she might be expected to meet a man. In circumstances where, for whatever reason, the mother was unavailable to perform this function, another woman, usually well-known to the family, was chosen. A chaperon was usually expected to be a married woman, although a respected, older unmarried or widowed woman (typically someone beyond child-bearing age) was often acceptable.
Chaperones were usually not required in situations where an unmarried woman’s father was able to accompany his daughter(s). Chaperones for young men were not commonly employed in Western society until the latter half of the 20th century, although depending on the precise nature of the business he was on, a young male who temporarily left the company of their parents would usually find himself under the supervision of coaches, employers or other such individuals (such personnel were not typically seen to be chaperones in the traditional sense).