cassock

Etymology

From Middle French casaque (“cloak”).

noun

1. An item of clerical clothing: a long, sheath-like, close-fitting, ankle-length robe worn by clergy members of some Christian denominations.
   In one of the aisles there was an elaborately carved confessional box and I recognised the village priest in his heavy mountain boots and black cassock as he entered it and drew the dark velvet curtains behind him. 1956, Delano Ames, chapter 13, in Crime out of Mind
   When leading worship, Elsie usually wore a long black cassock and preaching bands. This would, of course, save her from the worry of choosing a suitable costume. 2014, Alan Argent, Elsie Chamberlain: The Independent Life of a Woman Minister, Routledge, page 203
2. (obsolete) A military cloak or long coat worn by soldiers or horsemen in the 16th and 17th centuries.
3. (obsolete) A coarse, loose cloak or gown, worn by women, sailors, shepherds, countryfolk etc.