Hello!
There are 2 prime words for "bank"
بنك : which is pronounced same as Bank , but in Arabic.
مصرف : the origin word which is mentioned in Arabic dictionaries.
Both words are widely used allover Arab world.
In some Arabic countries بنك is the keymain word . In other countries مصرف is the main keyword.
مصرف is not only means "bank" but it is also means an exchange store , were ppl go to exchange $ to Euro for example or to cash checks..
Here is google trend comparing both of them:
http://www.google.com/trends?q=%D9%8...o=all&date=all