"Meng-an" is from the Mongol word for thousand, "mingghan" (see Military of the Yuan dynasty) while "mou-k'o" means clan or tribe.Groups of fifty households known as "p'u-li-yen" were grouped together as a "mou-k'o", while seven to ten "mou-k'o" formed a "meng-an", and several "meng-an" were grouped into a "wanhu", Chinese for Ten Thousand Households.