The name Dorwinion (originally Dor-Winion) goes back to the earliest periods of Tolkien's writing, but seems to refer to different regions in different sources. The only solid evidence for Dorwinion's final location comes from a map of Middle-earth created by Pauline Baynes following a label placed by Tolkien himself, which shows it at the mouth of the Celduin, on the shores of the Sea of Rhûn.

Dorwinion clearly translates as 'land of ...', but the -wini- element is difficult to interpret. In earlier uses, it's referred to as a land of vines, which matches well with the fact that it was famous for its wines, but it's unclear whether 'land of vines' (or 'land of wines') is intended as a direct interpretation of the name. Alternatively, Tolkien also made a rough note that the name was equivalent to 'Land of Gwinion' (implying youth, freshness or greenness, though 'Gwinion' here might conceivably be a personal name). These two interpretations are not necessarily at odds with each other; taking them together, the name Dorwinion might be interpreted as 'land of fresh green vines' or something similar.