CHAPERON, originally a cap or hood (Fr. chape) worn by nobles and knights of the Garter in full dress, and after the 16th century by middle-aged ladies. The modern use of the word is of a married or elderly lady (cf. "duenna") escorting or protecting a young and unmarried girl in public places and in society.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)