(Sorry if this seems like spam. I re-posted something written for another thread on similar subject)
The thing about acronyms (and really all names) is that they take on a life of their own and don't really have to be totally self-explanatory. Today everyone knows what SRT and DdRT mean even if, as Kevin points out they are misnomers. (DdRT is a special case of SRT). Also once learned and in common usage, the original derivation is not important. Really who cares what IBM stood for? We know who they are.
But in the spirit of Treebing, I'll toss some thoughts into the ring.
The "T" in SRT, dDRT is for Technique and we know what that means: particular tools, particular configurations. In this spirit, let SRT stand as a Static Rope Technique and let Ddrt stand as a doubled-back Dynamic Rope Technique (which, by the way, will become a rarity in the future used only when mechanical advantage is needed, much like the RADS 3-to-1 is a special technique for , say, limb-walking.)
Now comes the DRT issue. Unlike SRT and dDRT, the meaning of DRT is a bit vague in arborist circles because it's rarely used and unfamiliar. What it's really about is redundancy. (In computer circles, they call it HA - high availability) Technically, a second doubled-back dynamic line could be paired with a single strand static line, two static lines can be paired, and a lanyard can be paired with any other technique - and they'd all be redundant or HA versions of the specific techniques.
So with the introduction of the word redundant, or its synonym, highly available, you can say, "today I am climbing with redundant SRT lines", or redundant Ddrt lines etc.
The salient point is SRT implies certain tie ins, certain redirects, certain tools (RW, HH, RR) - fine. That would be equally true with or without redundancy. Redundancy is an independent orthogonal attribute that can be combined with the various "rope techniques".