The Eisenhowers had two sons. Doud Dwight "Icky" Eisenhower was born September 24, 1917, and died of scarlet fever on January 2, 1921, at the age of three; Eisenhower was mostly reticent to discuss his death. Their second son, John Eisenhower (1922–2013), was born in Denver Colorado. John served in the United States Army, retired as a brigadier general, became an author and served as U.S. Ambassador to Belgium from 1969 to 1971. Coincidentally, John graduated from West Point on D-Day, June 6, 1944. He married Barbara Jean Thompson on June 10, 1947. John and Barbara had four children: David, Barbara Ann, Susan Elaine and Mary Jean. David, after whom Camp David is named, married Richard Nixon's daughter Julie in 1968. John died on December 21, 2013.

What was Doud Eisenhower's nickname?