Comment by tome

This is just begging the question! So "restaurateur" was first, but did "restaurant" get an "n"? Why isn't it "restaurat"? The reason is that in French (ultimately from Latin) "-ateur" means "person who" and "-ant" means roughly "ing". So a "restaurater" is someone who restores and "restaurant" means "restoring" (i.e. a restoring soup, subsequently place).