I read this some where:

The logical explanation of the origin of the North American name of the dish is that it derives from potatoes that have been "fried in the French manner". The English verb fry is ambiguous: it can refer to both to sautéing and to deep-fat frying, while the French "pommes frites" ("fried potatoes") refers unambiguously to deep frying.

Some feel that the word "french" in "french fries" is refers to the verb "to french", which means "to cut in thin lengthwise strips before cooking" (Merriam-Webster's Collegiate Dictionary, Tenth Ed.) On the other hand, "to french" is defined as "to prepare, as a chop, by partially cutting the meat from the shank and leaving bare the bone so as to fit it for convenient handling" (Oxford English Dictionary) in other dictionaries, seeming to suggest that the meaning of this process is not necessarily as set as it may appear. In addition, the verb "to french" did not start appearing until after "french fried potatoes" had appeared in the English-speaking world.
The Belgians are noted for claiming that french fries are Belgian in origin, but have presented no absolute evidence; the French have also been cited as possible creators of the dish, though most in France associated fries with Belgium. The Spanish claim that the dish was invented in Spain, the first European country in which the potato appeared via the New World colonies, and then spread to Belgium which was then under Spanish rule. Whether or not french fries were invented in Belgium, they have become the national dish, and they are the "symbolic" creators, at least for the rest of Europe. French fries have gained international prominence perhaps partly due to their pre-eminence in fast-food menus, propagated by fast-food chains like McDonald's and Burger King (Hungry Jacks in Australia). This came about through the introduction of the frozen french fry invented by the J.R. Simplot Company in the early 1950's. Prior to the legendary handshake deal between Ray Kroc of McDonald's and Jack Simplot of the J.R. Simplot Company, fries were hand cut and peeled in the back of McDonald's stores, but the advent of the frozen product dovetailed with Kroc's need for quick prep products and expansion of his new franchise across America. In America, french fries are typically served with hamburgers, a latter-day descendent of the French "steak-frites" combination. They are also often eaten with meat, fish, and vegetables or by themselves. They also make up half of the classic food combinations fish and chips and "moules-frites", a popular Belgian dish consisting of steamed mussels and french fries.

Another claim is that the inclusion of the word "French" in the fried potatoes is most likely a confusion as to the nationality of those who introduced the food to American and Canadian soldiers in World War I. When American and Canadian soldiers were stationed in southern Belgium, where many major battles of World War I took place, they were served "pommes frites". Since the region of Belgium the soldiers were in was predominantly French-speaking, the soldiers brought the dish back to the United States as "french fries".