Gateau has wider applications in French, just as 'cake' does in English..can mean a savoury cake, a sweet or savoury tart, or a thin pancake." ---Oxford Companion to Food, Alan Davidson [Oxford University Press: Oxford] 1999 (p. Choux/ puff paste, sponge, French cremes, Gateau St. As time progressed, baking pans in various shapes and sizes, became readily available to the general public.
The first gateau were simply flat round cakes made with flour and water, but over the centuries these were enriched with honey, eggs, spices, butter, cream and milk.
From the very earliest items, a large number of French provinces have produced cakes for which they are noted.
In its northeastern Old French dialect from wasel it as borrowed into English in the thirteenth century, where it survived until the seventeenth century." ---An A to Z of Food and Drink, John Ayto [Oxford University Press: Oxford] 2002 (p.
138) "The word 'gateau' crossed the Channel to England in the early 19th century...
You will find references to him in French culinary history books.
Cake recipes, Fannie Farmer's Boston Cooking School Cook Book  What is the difference between cake, gateau and torte? It generally denotes items made with delicate ingredients which are best consumed soon after the confection is made (gateaux des roi).
Gateau is generally used for fancy, but light or rich, often with fresh decoration, such as fresh fruit or whipped cream.
Whereas a cake may remain fresh for several days after baking or even improve with keeping, a gateau usually includes fresh decoration or ingredients that do not keep well, such as fresh fruit or whipped cream.
Thus Artois had gateau razis, and Bournonnais the ancient tartes de fromage broye, de creme et de moyeau d'oeulz.