This study focuses on Solangi and Caule, two terms often appearing in thirteenth century Western and non-Western sources and never systematically studied, apart from some brief explanations in footnotes. In many cases the two terms have been considered mere synonyms both indicating Koryŏ; in other cases Solangi has been believed to refer to not-better-identified people gravitating to the area of Manchuria and the northern part of the Korean peninsula. After taking into consideration both Western and non-Western sources, this article concludes that, at least in the thirteenth century, it is very difficult to consider Solangi as a synonym both of Caule and “Koryŏ.” Instead, I hypothesize that the term Solangi may have referred to people different from the Koreans of that time. In contrast, there is a high probability that Caule is Koryŏ, and that the term Caule itself ended up indicating modern Korea.