In its native Germany in the late XIX century, the undercut was widely known as “the island haircut”, because the long lock of hair sitting on top of the shaved head looked like a small patch of land surrounded by water. The haircut took hold with British street gangs and crossed the Atlantic with Scottish and Irish immigrants.
The undercut was popular since the Edwardian era and dominated in Western Europe throughout the century predominantly among men. Usually, the hair on the top of the head is long and parted on either the side or center, while the back and sides are buzzed very short.
From the turn of the XX century until the 1920s, the undercut was popular among young working class men, especially members of street gangs.
In interwar Glasgow, Neds, the precursors to the Teddy Boys, favored a haircut that was long on top and cropped at the back and sides.
Despite the fire risk, lots of paraffin wax was used to keep the hair in place. Other gangs who favored this haircut were the Scuttlers of Manchester, and the Peaky Blinders of Birmingham, because longer hair put the wearer at a disadvantage in a street fight.
During the jazz age of the 1920s and 1930s, hairstyles of this type were considered mainstream fashion. In Nazi Germany, a version of this haircut which was long on top but shaved at the back and sides was popular among Wehrmacht officers. Beginning in the late 1980s, centrally parted undercuts, derived from the bowl cut, made a comeback among fans of new wave, synthpop, and electronic music as an alternative to the mullets and backcombed hair worn by glam metal bands and their fans.
The undercut went out of style with the start of the second millennium, but was revived in the early 2010s among the indie and skater subcultures that imitated the 1930s and 1940s versions: the top is longer and pomaded or combed to one side and shaved or clipped on the sides.