christened John, etc
Jeffrey Archer's "False Impression":
Anna smiled and, turning to Nakamura, said,"This is my friend, Jack Fitzgerald Delaney"
"No doult christened John," suggested Mr. Nakamura as he shook hands with Jack.
"Correct, sir"
"Names chosen by an Irish mother, or perhaps you were born on the twenty-second of November 1963?"
"Guilty on both counts," admitted Jack.
"Very droll"
question:
1. christened John,
2. why the name is chosen by an Irish mother
3. why " born on the twenty-second of Nov. 1963"
4. what does "both counts" mean here
5. droll?
thank you for you help

Question

christened John, etc
Jeffrey Archer's  "False Impression":
Anna smiled and, turning to Nakamura, said,"This is my friend, Jack Fitzgerald Delaney"
"No doult  christened John," suggested Mr. Nakamura as he shook hands with Jack.
"Correct, sir"
"Names chosen by an Irish mother, or perhaps you were born on the twenty-second of November 1963?"
"Guilty on both counts," admitted Jack.
"Very droll"
question: 
1. christened John,
2. why the name is chosen by an Irish mother
3. why " born on the twenty-second of Nov. 1963"
4. what does "both counts" mean here
5. droll?
thank you for you help

Answer

1. Christened John - given the Christian name of John in a Christian baptism ceremony, making him an official member of the church (as a baby). 
2. Delaney is an Irish name, and Irish mothers often choose the name of the baby.
3. John (Jack) Fitzgerald Kennedy, a beloved president and of Irish descent, was assassinated on twenty-second of November 1963.  I'm old enough to remember it.
4. Guilty on both counts - humorously admitting that yes, I was named by an Irish mother and yes, I was born on that date.  A count is a criminal count against a criminal.  A single crime can mean charging on more than one count (robbery and murder, for example).
5. Droll = oddly humorous or amusing.