It is not actually hemp, but named so because hemp was long a major source of fiber, and other fibers were sometimes named after it. The name refers to the capital of the Philippines, one of the main producers of Manila hemp.
The hatmaking straw made from Manila hemp is called Tagal or Tagal straw.
^"Manila hemp". Transport Information Service, Gesamtverband der Deutschen Versicherungswirtschaft e.V. Retrieved May 15, 2011.
^ abH. T. Edwards, B. E. Brewer, George E. Nesom, Otis Warren Barrett, William Scrugham Lyon, & Murad M. Saleeby (1904). "Abacá (manila hemp)". Farmers' bulletin (Bureau of Agriculture. Republic of the Philippines).