South Korea and South Korea are both on the Korean peninsula, but why are their names different?

After the end of the Korean dynasty, a modern country was established on the Korean peninsula, which was called "Great Korea and Imperial State".

Later, after World War II, North Korea established two countries with the 38th parallel as the dividing line. The establishment of the southern nation-state means the downfall of the monarch. Naturally, it cannot be called "Great Korea, Great Emperor and Great Nation", so it is called "Republic of Korea" for short: South Korea (South Korea cannot be called "Great Power" or "Republic of China" for short).

The northern part of the Korean peninsula was established-the Democratic People's Republic of Korea, or Korea for short.