One subset of Geographic descriptors are Ethnonyms, that is, the names of peoples, often self-selected, often official, sometimes historical and/or anachronistic, occasionally fictitious (Wakandans), but (hopefully) never perjorative. The number of ethnonyms that appear in the databases is more than 10,000, and even this is just a small part of the constantly multiplying numbers of ethnicities in the world. Some groups have recently been officially defined as ethnic groups, like Travellers in Ireland; others have gradually been recognized as something like an ethnic group, like Hippies; but some are too few, too scattered and too ephemeral to become ethnic groups, like Emos.
The purpose for this complex set of descriptors is to facilitate precise access to information on these numerous sub-populations. Happily, most of time these descriptors can be ignored.
There are many kinds of ethnonyms and many groups or individuals have several relevant ethnonyms. Many are not helpful, e.g., the British usage “Asian” for Pakistanis, but where such ambiguities exist, we use as many as we know about. Official usages are often unhelpful: Myanmar does not recognize the Rohingyas as a national minority, while the American majority population, officially Other-Non-Hispanic White-Other is increasingly self-identifying as European-American, or less commonly as Euro-American. (The older term “Caucasian” is dying out, especially since Caucasian ethnics like Chechens have dispersed worldwide.) At the same time, many governments carefully classify ethnicities as the basis for granting or withdrawing privileges. Frequently statistical tables of ethnicities in populations invent new categories just for that single table, probably because it simplified the construction of the table: In such cases we try to add more standard ethnic name(s) for the unique ethnic names in that table.
There are often problems in constructing hybrid ethnonyms, like former Peruvan Pres. Fujimori, who was Japanese-Peruvian, but sometimes there are common usages, like Polish-Jews. (But in the United States: Jewish-Americans.) And people with multiple ethnicities might get more than one ethnonym to facilitate retrieval: so a Japanese-Brazilian person who moved to France would be a French-Japanese-Brazilian and Japanese-Brazilian, but if they move to Japan simply Japanese-Peruvian. However, as such multiple ethnicities start to undergo a combinatoric explosion there is a practical limit to parsing identities, although some, like African-American-Muslims, remain common.
At the same time, such ethnicity information is often very elusive and many governments and news services completely suppress such information.