▁▁ ▁This ▁name , ▁Four ▁Se as ▁( ; ▁), ▁is ▁sometimes ▁used ▁to ▁refer ▁to ▁the ▁world , ▁or ▁simply ▁China , ▁which ▁is ▁perce ived ▁as ▁the ▁civil ized ▁world . ▁It ▁came ▁from ▁the ▁ancient ▁notion ▁that ▁the ▁world ▁is ▁flat ▁and ▁surrounded ▁by ▁sea . ▁ ▁Han ▁▁ ▁The ▁name ▁Han ▁(/ ; ▁) ▁der ives ▁from ▁the ▁Han ▁dynast y ▁( 2 0 6 ▁BC – 2 2 0 ▁AD ), ▁who ▁pres ided ▁over ▁China ' s ▁first ▁" g old en ▁age ". ▁The ▁Han ▁dynast y ▁col lapsed ▁in ▁ 2 2 0 ▁and ▁was ▁followed ▁by ▁a ▁long ▁period ▁of ▁dis order , ▁including ▁Three ▁Kingdom s , ▁Six teen ▁Kingdom s , ▁and ▁Southern ▁and ▁Northern ▁D ynast ies ▁periods . ▁During ▁these ▁periods , ▁various ▁non - Ch inese ▁eth nic ▁groups ▁inv aded ▁from ▁the ▁north ▁and ▁conquer ed ▁areas ▁of ▁North ▁China , ▁which ▁they ▁held ▁for ▁several ▁centuries . ▁It ▁was ▁during ▁this ▁period ▁that ▁people ▁began ▁to ▁use ▁the ▁term ▁" H an " ▁to ▁refer ▁to ▁the ▁n atives ▁of ▁North ▁China , ▁who ▁( un like ▁the ▁inv aders ) ▁were ▁the ▁descend ants ▁of ▁the ▁subjects ▁of ▁the ▁Han ▁dynast y . ▁ ▁During ▁the ▁Y uan ▁dynast y ▁Mong ol ian ▁r ul ers ▁divided ▁people ▁into ▁four ▁classes : ▁Mong ols , ▁Sem u ▁or ▁" Col our - ey eds ", ▁Hans , ▁and ▁" S ou ther ns ". ▁Northern ▁Chinese