I guess I should explain this in a little more detail. The usage describes the cultures/languages in which the name is currently primarily used. If the name is no longer used, then it can be slotted into one of the "ancient" categories. If the name is only really used in literature (eg the Tolkien names) then it goes into the "literature" category. Likewise for the "mythology" and "biblical" names. If the name is only used to refer to a historic person, doesn't fit into one of the ancient categories, and isn't commonly used as a given name then it goes into the "history" category (eg Napolean, Attila). The "theology" category is reserved for a few select names that don't fit elsewhere.
Every other category should be self-explanatory. However, one note on the Welsh/Scottish/Irish categories -- Since a great deal of English names are also used in Wales, Scotland, and Ireland I am only classifying names as such when they are distinctively Welsh, Sco, or Irish.
Here's a list of the categories:
African
New World Mythology
Armenian
Basque
Biblical
Biblical (Variant)
Breton
Bulgarian
Catalan
Ancient Celtic
Ancient Celtic (Latinized)
Celtic Mythology
Celtic Mythology (Latinized)
Chinese
Judeo-Christian-Muslim Legend
Croatian
Czech
Danish
Dutch
Ancient Egyptian
Egyptian Mythology
Egyptian Mythology (Hellenized)
English
English (Modern)
Anglo-Saxon
Anglo-Saxon (Latinized)
Medieval English
Anglo-Saxon Mythology
Esperanto
Far Eastern Mythology
Finnish
French
Frisian
Galician
German
Ancient Germanic
Ancient Germanic (Latinized)
Germanic Mythology
Greek
Ancient Greek
Ancient Greek (Latinized)
Ancient Greek (Anglicized)
Greek Mythology
Greek Mythology (Latinized)
Greek Mythology (Anglicized)
Hawaiian
History
Hungarian
Icelandic
Indian/Hindu
Hindu Mythology
Iranian
Irish
Irish Mythology
Italian
Japanese
Jewish
Khmer
Korean
Latvian
Lithuanian
Literature
Manx
Maori
Muslim
Mythology
Near Eastern Mythology
Near Eastern Mythology (Hellenized)
Norwegian
Pacific/Polynesian
Polish
Portuguese
Provençal
Romanian
Ancient Roman
Late Roman
Roman Mythology
Russian
Scandinavian
Ancient Scandinavian
Old Norse Mythology
Scottish
Serbian
Slovak
Slovene
Spanish
Swedish
Theology
Turkish
Ukrainian
?
Vietnamese
Welsh
Welsh Mythology