What is "geomungo"

The geomungo (also spelled komungo or kŏmun'go) or hyeongeum (literally "black zither", also spelled hyongum or hyŏn'gŭm) is a traditional Korean stringed musical instrument of the zither family of instruments with both bridges and frets. Scholars believe that the name refers to Goguryeo and translates to "Goguryeo zither" or that it refers to the colour and translates to "black crane zither" (hyeonhakgeum, 현학금 / 玄鶴琴).