What does dd stand for?

I know very well what the command does, but man dd, info dd tell me: 'Convert and copy a file', as does GNU Coreutils . Google says its an abbreviation of everything between medicine and bad webchat slang; except someone saying it means 'data destroyer', something used in PC forensics - I'd be horrified if my dd destroyed _my_ data! Any insight? :-) --- **Update**: Of course I had to check the jargon file : > The Unix dd(1) was designed with a > weird, distinctly non-Unixy keyword > option syntax reminiscent of IBM > System/360 JCL (which had an elaborate > DD ‘Dataset Definition’ specification > for I/O devices) Still sounds pretty ambiguous, but then it says: > though the command filled a need, the interface design was clearly a prank. Heh :-)