The fishtail jacket is having a serious moment these days. And while the origin of the name ain’t all that hard to deduce, you may be wondering about the origin of the style itself. Here goes: In 1948 the military devised a cold-weather jacket that split into “tails” at the back that could be wrapped around the wearer’s legs and cinched tight with drawstrings for extra insulation. In 1951 these jackets—christened the M51—were mass-produced and issued to soldiers en route to Korea (either on foot, or dropped out of airplanes when the fishtail functionality would conveniently keep the bottom of their parkas from flapping wildly in the wind). London mods co-opted the M51 for their own sartorial purposes in the sixties, and their descendants are doing the very same right now.