From Hull AWE
Ethnonym is a common noun which denotes 'the name of an ethnic group or a people', and particularly the name used by an ethnic group or people (in its own language[s]) to denote itself.
Other words have been used:
- Demonymic: originally 'a name formed from the Greek δῆμος (demos, 'deme', 'administrative district') to which the bearer of the name belonged'. (The use of a demonymic replaced that of a patronymic in ancient Athens as one of the reforms of Cleisthenes c.508-7 BCE.) Because of its technical use in the study of ancient history and classical studies, AWE does not recommend this term in the sense given above for ethnonym. The use of demonymic in this sense is dated to 1990, when it was used by Paul Dickson in What do you call a person from ...? (]).
- Gentilic has been used to mean what AWE prefers to call an 'ethnonym'. 'Gentilic' has a principal meaning, akin to that of gentile, of 'tribal', 'national', which quickly developed a pejorative meaning of 'pagan', 'heathen' (in other words despising those who are not of 'our' tribe or nation). For this reason AWE prefers not to use gentilic as a technical term in linguistics. (See also gentle - gentile.) Gentilic has been used in several different forms, all of which are obsolete and have never been common. (OED defines then by reference to each other.)
- Toponym is more precisely used to mean "A place-name; a name given to a person or thing marking its place of origin" (OED) - in other words, not necessarily a name derived from the name of an ethnic group. It is the more general usage that leads AWE to prefer not to use the term. (It is true that the names of some places are linked to the names of the ethnic group that occupied them, as the name 'England' is derived from that of the 'Angles', who settled in southern Britain during the fifth and sixth centuries.)