Q. Are English translations of Native American terms for place-names treated like proper nouns and capitalized? For example, would you refer to Dook’o’oosłííd (Diné for Gleaming Summit)? Or should it be Dook’o’oosłííd (Diné for gleaming summit).
A. In your example, we would use lowercase and quotation marks for the translated term in parentheses (see also CMOS 11.5): Dook’o’oosłííd (Diné for “gleaming summit”). We’d capitalize it (and drop the quotation marks) only if the place is known in English by the translated name. For example, you might refer to Firenze (Italian for Florence).
Or, drawing on information from the US Forest Service (which translates Dook’o’oosłííd as “the summit which never melts” or “the mountain which peak never thaws”), you could refer to Dook’o’oosłííd (the Diné name for the San Francisco Peaks) or to the San Francisco Peaks (Dook’o’oosłííd in Diné).