The term “French fried potatoes” first appeared in print in 1856.
The wording is found in Eliza Warren’s cookbook Cookery for Maids of All Work. Her recipe describes cutting new potatoes into thin slices, frying them in boiling fat, salting them, and browning both sides.
This 1856 reference does not necessarily describe the thick, deep-fried potato batons now associated with fast-food French fries. It is closer to thin, shallow-fried slices. Earlier European recipes described fried potatoes in French, but the English phrase itself is documented in Warren’s book.
A common mix-up is Thomas Jefferson’s 1802 White House reference to potatoes served “in the French manner.” That is earlier evidence of a French-style fried-potato dish in America, but it is not the first known printed use of the specific English term “French fried potatoes.”