Interessant. Deutsche Dokumentationen / Woerterbuecher sagen Decision, englische eher day. Da es militaerische Rede ist, was sagt die Armee dazu:http://www.army.mil/cmh-pg/faq/ddaydef.htm
What does the "D" signify in D-Day, and the "H" signify in H-Hour?
The terms D-day and H-hour are used for the day and hour on which a combat attack or operation is to be initiated. They designate the day and hour of the operation when the day and hour have not yet been determined, or where secrecy is essential. The letters are derived from the words for which they stand, "D" for the day of the invasion and "H" for the hour operations actually begin. There is but one D-day and one H-hour for all units participating in a given operation. It is unnecessary to state that H-hour is on D-day.
und ausserdem: http://www.pbs.org/wgbh/amex/dday/sfeature/sf...
The Meaning of the "D"
Ever since June 6, 1944, people have been asking what the "D" in "D-Day" means. Does it stand for "decision?" The day that 150,000 Allied soldiers landed on the shores of Normandy was certainly decisive. And with ships, landing craft and planes leaving port by the tens of thousands for a hostile shore, it is no wonder that some would call it "disembarkation" or "departed."
There is not much agreement on the issue. But the most ordinary and likely of explanations is the one offered by the U.S. Army in their published manuals. The Army began using the codes "H-hour" and "D-day" during World War I to indicate the time or date of an operation's start. Military planners would write of events planned to occur on "H-hour" or "D-day" -- long before the actual dates and times of the operations would be known, or in order to keep plans secret. And so the "D" may simply refer to the "day" of invasion.