Why the difference in metal between 銀行 and お金?


Money seems to be about gold but banks about silver. Is this due to an
evolution of the status of the valuable metals themselves? Is it a complicated
(e.g. ateji) etymology?




Firstly, the native word
[金（かね）](https://dictionary.goo.ne.jp/jn/43677/meaning/m0u/%E3%81%8B%E3%81%AD/)
in お金 only means _metal_ and **not** _gold_. You may have mixed it up with the
Sino-Japanese
[金（きん）](https://dictionary.goo.ne.jp/jn/58723/meaning/m0u/%E3%81%8D%E3%82%93/)
that means _gold_ (it also means _metal_ as a morpheme, but not for a
standalone word). The native word for _gold_ is
[こがね](https://dictionary.goo.ne.jp/jn/76300/meaning/m0u/%E3%81%93%E3%81%8C%E3%81%AD/)
"yellow-metal". Thus money is called お金 just because coins are made of metals.
No mystery :)

On the other hand, 銀行 is [a relatively newly imported
word](http://yain.jp/i/%E9%8A%80%E8%A1%8C) from Chinese originally means 銀
"silver" + 行 "guild". What was traditionally the standard money in Japan is [a
quite debatable
topic](https://ja.wikipedia.org/wiki/%E6%97%A5%E6%9C%AC%E3%81%AE%E8%B2%A8%E5%B9%A3%E5%8F%B2)
(gold, silver, copper, or rice??), but China has a long tradition of silver
standard system, so that's why silver is the synonym of money for them.

