The Titles of Nobility Amendment

"In 1810 Maryland Sen. Philip Reed introduced the Titles of Nobility Amendment, which would have revoked citizenship from any American who accepted a title of nobility from a foreign country. You might be wondering, "What's the big deal?" — and you wouldn't be alone.

For many years even historians couldn't figure out the motivations behind the amendment."
https://people.howstuffworks.com/10-weirdest-failed-constitutional-amendments1.htm

"The Titles of Nobility Amendment is a proposed amendment to the United States Constitution. The 11th Congress passed it on May 1, 1810, and submitted to the state legislatures for ratification. It would strip United States citizenship from any citizen who accepted a title of nobility from an "emperor, king, prince or foreign power." On two occasions between 1812 and 1816, it was within two states of the number needed to become part of the Constitution. Congress did not set a time limit for its ratification, so the amendment is still pending before the states. Ratification by an additional 26 states is now needed for its adoption."
https://en.wikipedia.org/wiki/Titles_of_Nobility_Amendment

The case of the missing 13th amendment to the Constitution

"A few years ago, a group of Iowa Republicans claimed the legitimate 13th Amendment to the Constitution was “missing.” The debate is part of a historical detective story with some surprising twists that is still taking place."
https://constitutioncenter.org/blog/the-case-of-the-missing-13th-amendment-to-the-constitution

"If any citizen of the United States shall accept, claim, receive or retain, any title of nobility or honour, or shall, without the consent of Congress, accept and retain any present, pension, office or emolument of any kind whatever, from any emperor, king, prince or foreign power, such person shall cease to be a citizen of the United States, and shall be incapable of holding any office of trust or profit under them, or either of them."
https://concurringopinions.com/archives/2017/07/the-titles-of-nobility-amendment.html

"The Titles of Nobility Amendment (known as the Missing 13th Amendment by pseudolaw practitioners and those who like to confuse people) is one of the numerous failed amendments to the Constitution. The real 13th Amendment ended slavery. The proposed amendment was approved by the United States Congress in 1810 and was sent to the states for ratification; while 12 states ratified the amendment it never passed the required threshold to be added to the Constitution."
https://rationalwiki.org/wiki/Titles_of_Nobility_Amendment