classifier for cloth or paper, width

幅 is composed of 巾 (cloth) and 畐 (filled). 巾 represents cloth or fabric, while 畐 carries the meaning of fullness or completeness. Therefore, 幅 conveys the idea of the width of a piece of cloth when it is fully spread out. Later, it came to broadly refer to the width of anything, and is also used as a measure word for cloth or paper.