The standard four food groups are based on American agricultural lobbies. Why do we have a milk group? Because we have a National Dairy Council. Why do we have a meat group? Because we have an extremely powerful meat lobby.
A figure of speech in which one word is substituted for another with which it is closely associated. For example, in the expression The pen is mightier than the sword, the word pen is used for "the written word," and sword is used for "military power."