character used in place names
This rare kanji has no clear standalone meaning. It is used in place names, so treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines 土 (earth) with 亞, but the original semantic or phonetic role of 亞 in this character is unclear.
The left side is earth 土, and the right side is 亞. Since it appears in place names, imagine a map where a place is marked with a cross-like 亞 shape on the ground.
For オ, picture an old map where a place name is marked with an 'O' symbol: O -> オ, and the earth 土 beside 亞 marks the spot.