[Beck]

The traditional designations like DD for destroyers had nothing to do with the number of letters or their presence in the word. Rather it was a means to differentiate from like types of vessels. There were only so many hull types on which a vast number of different ships were based. To be able to distinguish between them a system was created using letters for designations. All had a minimal of two letter designation with the first letter being the base designation and the second being a suffix (or it could have mutliple suffixes like CLAA - light cruiser, anti-aircraft). The base designation served to let one know the general type of the vessel, ie. destroyer, cruiser, battleship, etc. with the second serving to distinguish from the different types/roles of vessels. DD was used to designate a basic destroyer. The repeat of the letter always served to note the basic ship type. A derivative of the destroyer was the DE or destroyer escort which was used to escort and supply anti-submarine capability to those being escorted. Carriers used CV, not because carrier begins or has the letter c in it, but because the early carriers were based on cruiser hull designs and hence were considered a cruiser derivative. The suffix V came to use because that letter was assigned to serve as the suffix for vessels having fixed wing aircraft. The suffix S in your use of DS for destroyer would imply that it was a destroyer seaplane tender and not a destroyer.