well lets see... it can be the initials to the first four presidents of the US. George Washington, Jonh Adams, Thomas Jefferson, James Madison... i know.
The President with the nickname the butcher was Ulysses S. Grant. Another common nickname for him was Sam as his initials U.S. stood for Uncle Sam.
Rutherford Birchard Hayes has those initials.
Theodore Roosevelt
Cabinet initials since 1979 are HHS.
Andrew Jackson
The initials of Ronald Reagan, who is considered the 40th U. S. President, are R.W.R.
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Nelson Rockefeller
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Harry Truman. The S. didn't stand for anything.
The 26th presidents full name was Theodore Roosvelt Jnr. He was also known as TR or Teddy. He had no middle name, so he had only one initial: T for Theodore.
Herbert Hoover is the only president to have the initials HH. He was the 31st president of the United States and served from march 4, 1929 to march 4, 1933. The Hoover Dam in Nevada bears his name.
The airport code for Gray Army Airfield is GRF.
Your question is in the category of John F. Kennedy. But in case you still weren't sure, it stands for John Fitzgerald Kennedy.
No US president has I, ,X, Y , or Z among his initials.