What is "okjeo"

Okjeo was a Korean tribal state which arose in the northern Korean peninsula from perhaps the 2nd century BC to the 5th century AD.

Dong-okjeo (Eastern Okjeo) occupied roughly the area of the Hamgyŏng provinces of North Korea, and Buk-okjeo (Northern Okjeo) occupied the Duman River region.

Dong-okjeo was often simply called Okjeo, while Buk-okjeo was also sometimes referred to as Chiguru (置溝婁, 치구루) or Guru (구루), the latter name being also applied to Goguryeo. Okjeo bordered the other minor state of Dongye on the south, and shared a similar fate.