In Japan a triangle shaped kerchief is used for cooking and cleaning. Its purpose is hygiene. By the way it’s called, “sankaku (triangle) – kin (kerchief/cloth) in Japanese.
For example, people wear a triangular kerchief when they clean to keep hair clean from a dust falling. For cooking people wear it to avoid hair falling into foods. School kids wear a triangular chief when they serve lunch and clean at school.
On markets there are many triangle shaped clothes sold, but some people use square shaped cloth and fold them into a triangle shape.