A pigtail (also known as Twin Tail(ツインテール/TsuinTe-ru) in Japan) is another name for hair styled into a large braid that extends down or out from the head. In analogy to the ponytail hairstyle and the long, free-flowing tail of a horse, a pigtail is named for the visual resemblance of a thick, irregularly-tensioned hair braid to the kinked tail of a pig. A person's hairstyle may consist of one or more individual pigtails.
In some regional usages of English, pigtails are considered synonymous with a symmetric pair of hair bunches, regardless of whether each "bunch" is braided or left loose. This usage is not evident in American literature where one frequently finds references to "two pigtails" denoting two braids.
Within the UK, this styles is referred to as plaits.
From the later 1600s through the 1800s, the term came to be applied to any braided (plaited, in British parlance) hairstyle. The British army also adopted a single pigtail or "queue" as its standard dress for long hair.
Robert Louis Stevenson mentions "pigtail" referring to hair and then to "pigtail tobacco" in the first and fourth chapters of Treasure Island, respectively.
The term pigtail in British English does not convey a childish connotation. To the contrary, even to this day British barristers wear a wig with pigtails as a sign of their position and wisdom. In American English however, the childish connotation is evident. However, in American English, usage of the word "pigtails" to refer to unbraided bunches is also more common.