出典:Wiktionary
Borrowed from French restaurateur.
This is also spelled restauranteur (with an n), but this is considered erroneous by some, and the form restaurateur (without the n) is preferred in formal writing, and especially in the United Kingdom.[1]
The form restaurateur (without the n) is the earlier form, borrowed from French, while the form restauranteur (with an n) = restaurant + -eur (“(agent) one who”) is a later formation, from Anglicized forms, and thus seen by some as an etymological error.
However, restauranteur is widely used, and can be found in formal British writing.[2]