Dellorto isn't a "bicycle" carb per se, I believe they were used in motocross on a variety of mx bikes. The dax r/t carb is a dellorto clone btw.Good question. I'm not sure anyone knows. I always just assumed they were arbitrary initials given by whoever designed it.
The only bicycle carbs I know of are:
NT
NTTC
RT
CNS
Dellorto
You might be onto something with this!Dellorto has been making carbs since Hector was a pup. I have one on my '61 Capriolo, and they go back waaay before that.
NT = Not technical.
RT = Really terrible.
NTTC = Not terribly technical carb...
Just a guess.