Toponymy is the study of place names (toponyms), their origins, meanings, use and typology. The word "toponymy" is derived from the Greek words tópos (τόπος) ("place") and ónoma (ὄνομα) ("name"). Toponymy is itself a branch of onomastics, the study of names of all kinds.
Toponym is the general term for any place or geographical entity. Related, more specific types of toponym include hydronym for a body of water and oronym for a mountain or hill. A toponymist is one who studies toponymy.
According to the Oxford English Dictionary, the word "toponymy" first appeared in English in 1876; since then, toponym has come to replace "place-name" in professional discourse among toponymists. It can be argued that the first toponymists were the storytellers and poets who explained the origin of specific place names as part of their tales; sometimes place-names served as the basis for the etiological legends. The process of folk etymology usually took over, whereby a false meaning was extracted from a name based on its structure or sounds. Thus, the toponym of Hellespont was explained by Greek poets as being named after Helle, daughter of Athamas, who drowned there as she crossed it with her brother Phrixus on a flying golden ram. The name, however, is probably derived from an older language, such as Pelasgian, which was unknown to those who explained its origin. George R. Stewart theorized, in his book Names on the Globe, that Hellespont originally meant something like "narrow Pontus" or "entrance to Pontus", "Pontus" being an ancient name for the region around the Black Sea, and by extension, for the sea itself.
Place names provide the most useful geographical reference system in the world. Consistency and accuracy are essential in referring to a place to prevent confusion in everyday business and recreation. A toponymist, through well-established local principles and procedures developed in cooperation and consultation with the United Nations Group of Experts on Geographical Names (UNGEGN), applies the science of toponymy to establish officially recognized geographical names. A toponymist relies not only on maps and local histories, but interviews with local residents to determine names with established local usage. The exact application of a toponym, its specific language, its pronunciation, and its origins and meaning are all important facts to be recorded during name surveys.
Scholars have found that toponyms provide valuable insight into the historical geography of a particular region. In 1954 F. M. Powicke said of place-name study that it "uses, enriches and tests the discoveries of archaeology and history and the rules of the philologists". Toponyms not only illustrate ethnic settlement patterns, but they can also help identify discrete periods of immigration.
Toponymists are responsible for the active preservation of their region's culture through its toponymy. They typically ensure the ongoing development of a geographical names data base and associated publications, for recording and disseminating authoritative hard-copy and digital toponymic data. This data may be disseminated in a wide variety of formats, including hard-copy topographic maps as well as digital formats such as geographic information systems and Google Maps.