"Water" is a common name in China. It was originally called "water" because of the fineness of silver. When the silver is insufficient, it should be replenished. This is called "slurry water". Later, all the documents they filled in were water bills.

The word "memo" comes from Shanghai, because all foreign exchange used to go through waterways, so it is commonly known as memo, which extends to this point (it sounds rational).

In the past, due to the underdeveloped information technology, foreign exchange transactions between China and other countries had to be transported by water, so it was called "water bill" and has continued to this day. A water bill is a general term for foreign exchange receipts, which is a process of changing water and foreign currency in different places.