The Greek name Aithiopia (Αἰθιοπία, from Αἰθίοψ, Aithiops, 'an Ethiopian') is a compound derived of two Greek words: αἴθω (aitho, 'I burn') + ὤψ (ops, 'face'). According to the Perseus Project, this designation properly translates in noun form as burnt-face and in adjectival form as red-brown.[4][5] As such, it was used as a vague term for dark-skinned populations since the time of Homer.[lower-roman 1][6] The term was applied to such peoples when within the range of observation of the ancient geographers, primarily in what was then Nubia. With the expansion of geographical knowledge, the endonym successively extended to certain other areas below the Sahara.