A revers or rever is a garment or part of a garment that is reversed to display the lining or facing outside. The word is a corruption of reverse. This is most commonly the lapels or cuffs, and the term is mostly used when they are made in a contrasting material. The term became current in the late 1860s at the time when dress coats were no longer buttoned up but worn with the lapels opened up and turned back, thus the revers was one of the few opportunities for adornment on the otherwise plain black coat.
In the 1890s a small 'jaunty' jacket with each lapel turned fully back was termed a 'rever'.
- Oxford English Dictionary