Why do we say "Korea"? Where does it come from? Since 한국사람들이 say 한국... - and 대한민국.
May you please tell me something about it?

See a translation

okay. let's talk about korean history. in 918 wang gun founding a country named "Goryeo" it's comming from ancient country name "Goguryeo" and that country is very opened country so they trade with not only japan, china but also arab's country so they called Goryeo as corea, coreano. and after Goryeo is destoryed by their own people. they founding another country named "Joseon" and Joseon, not like Goryeo. is very closed counry. they only trade with near country like china, japan. so they(arab and other country) remember us as corea not joseon. and this is the reason why u guys call us corea(korea)

and hangook, daehanmingook is from han. country of our ancestors, so we call ourself han nation. so 한국 mean country of han, and 대한민국 mean the great republic of han.

u know german people call theirself "Deutschland" or "Bundesrepublik Deutschland".
but other country call u guys like "germany" or "The Federal Republic of Germany" it's same as that