In Okinawan, nishi meant "north" rather than "west" as it does in standard Japanese, so Nishihara means "northern field" in respect to its position from the old Ryūkyū Kingdom capital at Shuri; in contrast, the Okinawan word for "west" is iri, which appears in the name of Iriomote-jima.
Gusuku (城) meaning "castle" is also common in place names in Okinawa, found in Tomigusuku, Nakagusuku, and Kitanakagusuku, among others.
The following encyclopedias and dictionaries are major research tools for reading and understanding Japanese place names and histories.
Each entry simply lists the reading of place name, its kanji, location, and longitude-latitude coordinate.
Dai Nihon Chimei Jisho (大日本地名辞書) is one of oldest, in 1907–1910, reprint and update version by 1971, published by Buzanbō (富山房).
The main editor was Tōgo Yoshida (吉田 東伍, 1864-1918) written in vernacular expression in Meiji period with each entry includes the history and folklore for name.
Konpakutoban Nihon chimei hyakka jiten (コンパクト版日本地名百科事典, Compact Land Japonica) Shogakukan in June 1998.
Based on the studies of geography and Japanese ancient words, each entry lists a few sentences about the origin and history of place names in gojuon order.