Originally Posted by knc1
"copy device" goes by the name 'dd' because the name 'cd' was already in use for a recognized purpose when "copy device" was written. So author just bump'd the first letter of the name one character.
I always heard it came from the IBM JCL
'DD' (Data Description) statement; that's why dd's syntax is so odd, compared to other Unix/Linux commands.
Having worked with JCL in my sordid past, I think it's rather likely; the syntax is certainly similar.