Question: The Canterbury cap is descended from an ancient headcovering originally worn where?

Context paragraphs:
Sakkos: The sakkos (Greek: σάκκος, "sackcloth") is a vestment worn by Orthodox and Greek Catholic bishops instead of the priest's "phelonion".  The garment is a tunic with wide sleeves, and a distinctive pattern of trim.  It reaches below the knees and is fastened up the sides with buttons or tied with ribbons.  It is similar in form to the western dalmatic, which is similarly derived from Byzantine dress.  The "sakkos" was originally worn by the Emperor as an imperial vestment, symbolizing the tunic of disgrace worn by Christ during his trial and mockery.

Nambawi: A nambawi is a type of traditional Korean winter hat worn by both men and women during the Joseon period for protection against the cold.  The other names for it are "pungdengi" and "nani" (literally warming ears).  The "nambawi" is also called "ieom" (literally "covering ears") which was worn in the early Joseon period, although it was derived from the cap.  It was originally worn by the upper class as a daily hat, but spread to commoners and women in the later period.  It was usually worn by middle-aged women and old people as well as by government officers who put it under the "samo" (사모, official hat).

Traditional Welsh costume: The traditional Welsh costume is a costume once worn by rural women in Wales.  It was identified as being different from that worn by the rural women of England by many of the English visitors who toured Wales during the late 18th and early 19th centuries.  It is very likely that what they wore was a survival of a pan-European costume worn by working rural women.  This included a version of the bedgown, originally worn by the gentry in the 17th and 18th centuries, an item of clothing that survived in Wales for longer than elsewhere in Britain.  The unique Welsh hat, which first made its appearance in the 1830s, was used as an icon of Wales from the 1840s.

Canterbury cap: The Canterbury cap is a square cloth hat with sharp corners found in the Anglican communion, similar to the Counter-Reformation's biretta, the notable exception being that a Canterbury cap has four ridges, compared to the biretta's three.  It is also soft and foldable, "Constructed to fold flat when not in use..." whereas the biretta is rigid.  The Canterbury cap is the medieval "birettum," descended from the ancient "pileus" headcovering.  It is sometimes called the "catercap."

American Civil War Corps Badges: Corps badges in the American Civil War were originally worn by soldiers of the Union Army on the top of their army forage cap (kepi), left side of the hat, or over their left breast.  The idea is attributed to Maj. Gen. Philip Kearny, who ordered the men in his division to sew a two-inch square of red cloth on their hats to avoid confusion on the battlefield.  This idea was adopted by Maj. Gen. Joseph Hooker after he assumed command of the Army of the Potomac, so any soldier could be identified at a distance.

Hwa: Hwa are a type of traditional Korean boot, which, along with "yi" (이), is a subdivision of Korean shoes.  The "yi" refers to all kind of shoes that do not go up to ankle.  "Hwa" are usually made of leather, and artisans who make the shoes are called "hwajang" (화장).  It was originally worn by northern kingdoms of Korea.  The horse-riding cultures of the North appear to have typically worn leather boots (hwa), while the farmers of the South wore shoes of leather or straw (hye).  Different types of boots were worn by military and civil officials.

Bonnet (headgear): A bonnet is any of a wide variety of headgear for both sexes—more often female—from the Middle Ages to the present.  It is impossible to generalize as to the styles for which the word has been used any more than for the hat and cap, but there is for both sexes a tendency to use the word for styles in soft material and lacking a brim.  Yet the term has also been used, for example, for steel helmets.  This was from Scotland (in 1505), where the term has long been especially popular.  "Bonnet" derives from the same word in French, where it originally indicated a type of material.  In the 21st century, only a few kinds of headgear are still called bonnets, most commonly those worn by babies and Scottish soldiers.  In addition, bonnets are worn by women as a Christian headcovering in some denominations.

Busby: Busby is the English name for the Hungarian "prémes csákó" ("fur shako") or "kucsma", a military head-dress made of fur, originally worn by Hungarian hussars.  In its original Hungarian form the busby was a cylindrical fur cap, having a bag of coloured cloth hanging from the top.  The end of this bag was attached to the right shoulder as a defence against sabre cuts.  In Great Britain busbies are of two kinds: (a) the hussar busby, cylindrical in shape, with a bag; this is worn by hussars and the Royal Horse Artillery; (b) the rifle busby, a folding cap of astrakhan (curly lambswool) formerly worn by rifle regiments, in shape somewhat resembling a Glengarry but taller.  Both have straight plumes in the front of the headdress.

Pileus (hat): The pileus ( – "pilos", also pilleus or pilleum in Latin) was a brimless, felt cap worn in Ancient Greece and surrounding regions, later also introduced in Ancient Rome.  The Greek πιλίδιον ("pilidion") and Latin "pilleolus" were smaller versions, similar to a skullcap.

Canadian military fur wedge cap: The Canadian military fur wedge cap, "envelope busby", or colloquially "The Astrakhan" is a uniform hat worn by the Canadian military and RCMP.  The outside of the cap is entirely covered in real (e.g. seal skin or Persian lamb) or synthetic fur and is shaped like a wedge.  When not being worn the cap folds flat.  The cap is about 8 in high but is normally worn with the apex of the wedge shape depressed back into the interior of the cap to form a longitudinal trough at the crown, reducing the overall height.  Often the cap is patterned such that the front of the crown will be slightly higher than the back.  On one side of the military style fur wedge cap hangs a flat flap made of cloth or wool that extends from the crown to the bottom of the cap, known as the "bag".  The colour of the "bag" was determined by the regimental colours (e.g. the RCMP bag was yellow).  The bag is very similar to that worn with the busby.  Because of the cap's passing resemblance to the hussar busby author and researcher James J. Boulton dubbed it the envelope busby.  Still, whatever influence the busby may have had on its design, the fur wedge cap pattern was "distinctly Canadian"

Supporting paragraphs: Canterbury cap Pileus (hat)
Answer: Ancient Greece