What does D-Day stand for?
The D in D-Day is the same than the H in H-Hour. It refers to military vocabulary. It is also possible to say : Y-Year.
The French army uses the same system which results to: Jour-J, Heure-H or Année-A.
Soldiers use the first letter of the word in order to say : THE moment. Here, in the case of the landing of Normandy, it means THE moment of the attack. It is a code name and thanks to this code there is no need to say the exact date. Thus it is possible to say “D-Day + 5” for : the date of the attack + 5 days.
This code avoids the ennemy intelligence to find too easily the right date or the right hour of the offensive.