Why is 河原 in 河原町 pronounced "Kawara" as opposed to the expected "Kawabara/Kawawara"?


The Kawaramachi St in Kyoto is spelled with 河原, /kawa/ and /hara/. I'd suspect
the two inner syllables to be merged into one mora at some point in history,
but do we have a record of when that happened?

Further question: how old are the current street names and machi names in
Kyoto generally?




かわら is a [normal noun](https://jisho.org/word/%E6%B2%B3%E5%8E%9F) meaning
"river beach". That is, when 河原 is used as a normal noun, it's always read as
かわら at least in modern standard Japanese. (For example 河原を歩く, 河原できれいな石を見つけた.)
That is the _expected_ reading. [This
古語辞典](https://kobun.weblio.jp/content/%E3%81%8B%E3%81%AF%E3%82%89) suggests
the word かわら existed at least 1000 years ago (except that it was written as
かはら in the historical kana orthography).

As an _exception_ , if 河原 is someone's family name or a place name, it may be
read as かわはら or かわばら.

