Poker glossary
John
John is slang for a jack. A pair of johns is a pair of jacks.
The simple explanation
If a player says he has 'two johns', he has a pair of jacks.
A closer look
The nickname is one of several for the jack, together with jake, hook and knave. It is table talk and does not change the rules or the card.
A practical example
A player says: 'I have a pair of johns in the pocket.' He holds J♥ J♦.
Full explanation
John is slang for a jack. A pair of johns is a pair of jacks.
John is slang for a jack.
It is table talk.
Other names for the jack are jake, hook and knave.
The card is the same.