John F. Kennedy was nicknamed Jack.
If John Tyler, John Adams, or John Quincy Adams was called Jack, it's not obvious.
US President John F. Kennedy was often referred to as Jack Kennedy.
John F. Kennedy was often called "Jack"/
Of course she did. Why else would she nickname her son Jack??
The Union Jack is the nickname of the UK flag.
Yes, Jack can be a common nickname for Jonathan.
'Jack' is a common nickname for someone whose name is 'John.'
His name was Jack Rackham. His nickname was Calico Jack
The nickname of Jill in the movie "Jack and Jill" is "Jilly."
JFK and Jack
The nickname for the British flag is the Union Jack. Although it is only correctly known as this when flown on a ship.
"Bubba" was the nickname for President Bill Clinton.
It was a Vice President, rather than a President, who had the nickname The Happy Warrior. The nickname belonged to Hubert Humphrey, the 38th Vice President of the United States.
I can find no record that any US President had this nickname.