This goes back to President Thomas Jefferson. While he was Ambassador to France, he enjoyed a side dish there known as "french fried potatoes". When he returned to the U.S., he served them at Monticello. By the 1870's they had become a delicacy. By 1900 they were a common dish. The name was shortened to "french frieds" in the 1920's, then to "french fries" in the 1930's. By the 1960's, it was often common to just call them "fries".
This Info From Ask The Meatman.com.