“The opera is named after the Emperor of Japan using the term mikado (御門 or 帝 or みかど), literally meaning “the honourable gate” of the imperial palace, referring metaphorically to its occupant and to the palace itself. The term was commonly used by the English in the 19th century but became obsolete.”
From Online Etymology Dictionary:
“1727, former title of the emperor of Japan, from mi “honorable” + kado “gate, portal.” Similar to Sublime Porte, old title of the Ottoman emperor/government, and Pharaoh, which literally means “great house.” “
“The literal meaning of 御門 is “the honorable gate”, that is, the gate of the Japanese imperial palace. The term was once used metonymically for the main occupant of the palace, thereby avoiding naming him directly, which was considered disrespectful. Compare Sublime Porte as a term for the Ottoman court and government, along with pharaoh (from Egyptian pr ꜥꜣ (“palace, pharaoh”, literally “great house”)) as a term for the Egyptian king.”
“A place is often used as a metonym for a government or other official institutions, for example, Brussels for the institutions of the European Union, The Hague for the International Court of Justice or International Criminal Court, Nairobi for the government of Kenya, the White House and Capitol Hill for the executive and legislative branches, respectively, of the United States federal government, or Foggy Bottom for the U.S. State Department. Other names of addresses or locations can become convenient shorthand names in international diplomacy, allowing commentators and insiders to refer impersonally and succinctly to foreign ministries with impressive and imposing names as (for example) the Quai d’Orsay, the Wilhelmstrasse, or the Porte.
A place can represent an entire industry: for instance, Wall Street, used metonymically, can stand for the entire U.S. financial and corporate banking sector. Common nouns and phrases can also be metonyms: “red tape” can stand for bureaucracy, whether or not that bureaucracy uses actual red tape to bind documents. In Commonwealth realms, The Crown is a metonym for the state in all its aspects.
In recent Israeli usage, the term “Balfour” came to refer to the Israeli Prime Minister’s residence, located on Balfour Street in Jerusalem, to all the streets around it where demonstrations frequently take place, and also to Prime Minister Bennett and his family who live in the residence.”