roll, scroll

卷 is composed of 龹 and the variant of 卩. 龹 is the picture of threshing, ancient Chinese use threshing machine to separate the grains from stalks, while the machine has wheel inside, so 龹 has the meaning of rolling or turning around. 卩 depicts a kneeling man, his knees are crooked. Both 龹 and 卩 has the meaning of 卷.