I'm probably very wrong but I had always had the documentally unsupported interpretation that the "d" stood for "delivery" or "doom" so delivery-day as in the delivery of the most lethal strike in history as if it were a long asked for package or order. (So for the allies, they believed the Reich had this coming and it was due time they "delivered" it)
The dooms-day wording being another way of saying judgement day just speaking to a damned one, or in other words a Nazi in the eye of an ally soldier. Doom's day being the day the nazies will be sent to hell.
Like I said however, I have no documented support on this but somehow I had always believed these were the reasons for the name D-Day. Open to critizism.
That's a fanciful notion, TGF, but only that. If you care to read the previous posts, there is enough helpful information there, including the true historical derivation. If you want to believe something else of course, that's up to you.
O-o-o-o..Mac..(brrr..shiver) Now what did I do with that winter coat.?