The cassock or soutane is a Christian clerical clothing coat used by the clergy and male religious of the Oriental Orthodox Churches, Eastern Orthodox Church and the Catholic Church, in addition to some clergy in certain Protestant denominations such as Anglicans and Lutherans. "Ankle-length garment" is the literal meaning of the corresponding Latin term, vestis talaris. It is related to the habits traditionally worn by nuns, monks, and friars.
The cassock derives historically from the tunic of classical antiquity that in ancient Rome was worn underneath the toga and the chiton that was worn beneath the himation in ancient Greece. In religious services, it has traditionally been worn underneath vestments, such as the alb.
In the West, the cassock is little used today except for religious services, save for traditionalist and those other Catholic clergy and religious who continue to wear the cassock as their standard attire. However, in many countries it was the normal everyday wear of the clergy until the 1960s, when it was largely replaced by clerical suits, distinguished from lay dress by being generally black and by a black shirt incorporating a clerical collar.
In Japan, male gakuran school uniform also inspired from cassocks.
The word cassock comes from Middle French casaque, meaning a long coat. In turn, the Old French word may come ultimately from Turkish kazak (nomad, adventurer – the source of the word Cossack), an allusion to their typical riding coat, or from Persian کژاغند kazhāgand (padded garment) – کژ kazh (raw silk) + آغند āgand (stuffed). The name was originally specially applied to the dress worn by soldiers and horsemen, and later to the long garment worn in civil life by both men and women. As an ecclesiastical term, the word cassock came into use somewhat late (as a translation of the old names of subtanea, vestis talaris, toga talaris, or tunica talaris), being mentioned in Canon LXXIV (74) of the Anglican 1604 Canons; and it is in this sense alone that it now survives.