Toponymy is the scientific study of place names (toponyms), their origins, meanings, use and typology. The word "toponymy" is derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 words tópos (τόπος) ("place") and ónoma (ὄνομα) ("name"). Toponymy is itself a branch of onomastics

Onomastics

Onomastics or onomatology is the study of proper names of all kinds and the origins of names. The words are from the Greek: "ὀνομαστικός" , "of or belonging to naming" and "ὀνοματολογία" , from "ὄνομα" "name". Toponymy or toponomastics, the study of place names, is one of the principal branches of...

, the study of names of all kinds. Toponymy is distinct from, though often confused with etymology

Etymology

Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

, which is the study of the origins of words.
A toponymist is one who studies toponymy.