Naengguk

Naengguk or chilled soup refers to all kinds of cold guk (국, soups) in Korean cuisine, mainly eaten in summer. It is also called chan'guk (찬국), which literally means "cold soup" in pure Korean, while the term naengguk is a combination of a hanja word (冷, "cold") and a pure Korean word (국, "soup"). The first historical record on naengguk appears in a poem written by Yi Kyu-bo (1168–1241), a high officer of the Goryeo period (918–1392). In the poem, naengguk is referred to as sungaeng (순갱), which literally means sunchaeguk (순채국), i.e., soup made with sunchae (Brasenia schreberi). Yi praised its clear and plain taste, saying it made usual dishes seem vulgar.

Source: Wikipedia