Nationality or ethnicity idioms

• Chinese walls - Chinese walls are regulatory information barriers that aim to stop the flow of information that could be misused, especially in financial corporations.
• Chinese whispers - (UK) When a story is told from person to person, especially if it is gossip or scandal, it inevitably gets distorted and exaggerated. This process is called Chinese whispers.
• Double Dutch - (UK) If something is double Dutch, it is completely incomprehensible.
• Dutch auction - If something is sold by setting a price, then reducing it until someone buys it, it is sold in a Dutch auction. It can also mean that something is changed until it is accepted by everyone.
• Dutch courage - Dutch courage is the reckless bravery caused by drinking too much.
• Dutch treat - If something like a meal is a Dutch treat, then each person pays their own share of the bill.
• Dutch uncle - A Dutch uncle is a person who gives unwelcome advice.
• Dutch wife - A Dutch wife is a long pillow or a hot water bottle.
• For England - (UK) A person who talks for England, talks a lot- if you do something for England, you do it a lot or to the limit.
• French leave - To take French leave is to leave a gathering without saying goodbye or without permission.
• Go Dutch - If you go Dutch in a restaurant, you pay equal shares for the meal.
• Good Samaritan - A good Samaritan is a persoon wh helps others in need.
• Greek to me - If you don't understand something, it's all Greek to you.
• If you'll pardon my French - (UK) This idiom is used as a way of apologising for swearing.
• Indian file - If people walk in Indian file, they walk in a line one behind the other.
• Indian giver - An Indian giver gives something, then tries to take it back.
• Indian summer - If there is a period of warmer weather in late autumn, it is an Indian summer.
• Like Chinese arithmetic - If something is complicated and hard to understand, it's like Chinese arithmetic.
• Mexican standoff - When there is a deadlock in strategy and neither side can do anything that will ensure victory, it's a Mexican standoff.
• More holes than Swiss cheese - If something has more holes than a Swiss cheese, it is incomplete, and lacks many parts.
• Perfidious Albion - England is known to some as perfidious Albion, implying that it is not trustworthy in its dealings with foreigners.
• Scotch Mist - The phrase 'Scotch mist' is used humorously to refer to something that is hard to find or doesn't exist - something imagined.
• Slow boat to China - This idiom is used to describe something that is very slow and takes a long time.
• Spanish practices - Unauthorized working methods that benefit those who follow them are Spanish practices.
• Stars and stripes - The stars and stripes is the American flag.
• Too many chiefs and not enough Indians - When there are too many chiefs and not enough Indians, there are two many managers and not enough workers to work efficiently.
• Young Turk - A Young Turk is a young person who is rebellious and difficult to control in a company, team or organisation. 

See http://www.usingenglish.com/reference/idioms/cat/6.html