The word manila in the name "manila folder" comes from manila hemp or abaca, from which manila folders were originally made.
The word you are looking for is ABACA.
manila hemp
Abaca is a plant native to the Philippines known for its strong and durable fibers. These fibers are commonly used in the production of ropes, twines, and textiles. Abaca is also known as Manila hemp.
They can be paper, silk or plastic. They can be a blend of wood and vegetable fibers. The vegetable fiber is bleached pulp abaca hemp, a small tree grown for its fiber.
Not always: manila hemp is a a natural fiber, so is cotton.
There is an image of manila hemp in related links.
The answer is abaca.It's five letters, ending in A. Abaca is a banana tree native to the Philippines. The leafstalks are processed into Manila hemp, which is used to make rope and paper.
'Manila hemp, also known as manilla, is a type of fiber obtained from the leaves of the abacá (Musa textilis), a relative of the banana. It is mostly used for pulping for a range of uses, including speciality papers. It was once used mainly to make manila rope,[1] but this is now of minor importance. Manila envelopes and manila paper take their name from this fibre.[2][3]It is not actually hemp, but named so because hemp was long a major source of fibre, and other fibres were sometimes named after it. The name refers to the capital of the Philippines, one of the main producers of abacá.[2][3]"Source: Wikipedia
abaka
A hemp refers to a certain fiber from certain plants, usually a reed plant. It is sometimes called jute or mourning cloth.
Candido Lopez Diaz is said to be the first Filipno inventor having invented a hemp fiber cleaning machine used in fabricating the Manila Hemp Rope, and in 1853 was awarded a gold medal by the Spanish Colonial Government in the Philippine Islands.