The word "Southern Sierra Miwok" is a language particular to California. In 1994 there were still 7 people that spoke this language. According to the UMLS, the name of the language is Meewoc and as Ethnologue provides it as one of the alternate names, it was possible to link this DefinedMeaning in the Community Database with the concept in the UMLS.
With 30.000 Expressions, there are many that also exist in the UMLS Authoritative Database. The UMLS has some 1.93 million Expression at the moment, and the first 200+ DefinedMeanings have already been linked. They are mainly US-American languages and chemical elements with an occasional animal like guinea pig thrown in for good measure.
It is relevant to have the concept linked. It means that the information in one database can be seen as supplementary to what is available in another database. Currently we have three databases, but when you consider how they are structured, there are implicit connections known as many of the concepts known in the UMLS are also known in the Swiss-Prot database. The only thing left doing is making them explicit. :)