(in the past) an older woman who, on social occasions, took care of a young woman who was not married （旧时未婚少女社交时的）年长女伴 a person who takes care of children in public, especially when they are working, for example as actors （尤指儿童表演时的）在场监护人 - (North American English)
a person, such as a parent or a teacher, who goes with a group of young people on a trip or to a dance to encourage good behaviour （未成年人集体旅行的）保护人，监护人；（未成年人舞会上的）行为引导人
Word Originlate Middle English (denoting a hood or cap, regarded as giving protection): from French, feminine of chaperon ‘hood’, diminutive of chape, from late Latin cappa ‘cap’. The current sense dates from the early 18th cent.