Manila

So, I'm at the supply closet, thinking, "Manila folders... manila folders... why manila?"

This is why (explanation courtesy of Wikipedia):

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 to make ropes and it is one of the most durable of the natural fibers, besides true hemp. Other uses for manila fiber are coarse fabric and paper, including Manila envelopes and Manila papers.

It is not really a hemp, but named so because hemp was for centuries a major source for fiber, so other fibers were sometimes named after it. The name refers to the capital of the Philippines. The country is one of the main areas of cultivation of abacá.