Origins and concept
Informally known as a "woobie", a poncho liner is a versatile field gear that were first used around 1962 by the U.S. special forces troops in the Vietnam War.
The woobie is a piece that can be attached to a standard issue poncho to provide additional warmth, as well as being usable as a blanket, sleeping bag or protective cover.
It consists of quilted nylon with a polyester filling. It is attached to the poncho by means of integral lengths of material which are looped through the poncho's eyelets.
From where come the term woobie?
The first ones were Olive Drab on both sides and the earliest models featured squared corners. Around 1963, a second model was fielded which was made of WWII duck-hunter patterned parachute fabric. This model required the standard "center seam" because the fabric wasn't wide enough to produce the entire width. Later, the first camouflaged pattern was produced which was named, "ERDL Pattern."
This stood for Engineer Research and Development Laboratories and the acronym became the common name for the pattern, which was enlarged somewhat in the 1980s to become the Woodland Pattern used on the BDU uniform and late 1980s poncho liners. The center seam was abandoned in the early 1970s because fabric could be produced in bolts that were wide enough that this sewing pattern was now obsolete.
Until the USMC produced their own Digital Woodland Pattern, most poncho liners were produced with the same pattern on both sides. The Marines decided to field one with Woodland Pattern on one side and a solid Coyote Color on the other. There are examples of improved models, which included high-tech 3M fillers (Thinsulate and the like), border and head zippers (there is no hole for one's head on standard issue poncho liners), and a variety of colors and patterns. Brigade Quartermaster, Inc. used to sell a zipper modification kit, which essentially codified and standardized commonly made modifications. Most recently, there have been models produced and issued in the Army's Universal Combat Pattern, the USAF's Environmental Camouflage Pattern, and Multicam/Scorpion.
Why are woobies loved products?
Woobies are a very useful piece of equipment, light and packable yet reasonably warm. Even when soaking wet, the poncho liner wrapped around you would trap body heat.
Because of this there is many people that custom their woobies into smoking jackets, hoodies, blanket coats or robes.
The poncho liner found wide acceptance amongst US troops in Vietnam, providing just enough warmth for cool tropical nights but still being light and small. It is especially popular today in the age of 100-pound rucks and bulky Modular Sleep Systems.