What does the D in D-Day stand for?

Question

coz wiki only said that it meant day of days, but when they say it's D-Day for someone - ?

Answer 1

Doomsday.

Answer 2

It can mean a few things.

Day of Days.

Dooms Day.

Decimal Day.

Death Day.

As a military term, it is usually just used to abbreviate itself.  They use this for secrecy reasons.  For example, "We will attack on the H-Hour, of the the D-Day, of the M-Month."

Answer 3

I believe it was a code name for the plan to invade Normandy during World War 2 The actual plan was called Operation Overlord.

As an expression it, D-Day means final judgement eg the day you receive your exam marks