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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 :-)

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dd is particularly good at destroying data if you aren't careful. "Data Destroyer" is not really a misnomer. – LawrenceC Aug 14 '12 at 3:25
up vote 20 down vote accepted

Wikipedia (dd) asserts it was named after IBM JCL command DD which stands for Data Description. I always thought it would mean data duplicate, though.

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It also says It is jokingly said to stand for "disk destroyer", "data destroyer", or "delete data" - cross referencing this with the Jargon file clicks a switch, I believe this is the answer we're looking for! – invert Feb 2 '11 at 20:49
It was definitely Dataset Definition. Dataset was the IBM term for File. In JCL you needed to write a DD record to define the file that you wanted to use and give a 2 character unit number code to reference in your Open statements. – Michael Dillon Feb 4 '11 at 2:44
//SYSUT1#3 DD DISP=(SHR,KEEP),DSN=DDAG.D1006Y00.SHT.APPLTN.NAMES ...(some real JCL, with a real 'IBM' DD :) ..There is no way it is relatd to the nix 'dd' ..BTW, the '//' is not a comment indicator – Peter.O Feb 5 '11 at 11:32
Can you add a reference? – mikemaccana Apr 5 '15 at 16:49
On the topic of the cc/dd name: Spurious. dd was always named after JCL dd cards. -- Dennis Ritchie (alt.folklore.computers, 2004) – mr.spuratic Oct 25 '15 at 19:39

Though the “best answer” was given, this site states otherwise:

Actually, it stands for ‘Copy and Convert’ and was renamed to dd only because cc was reserved for the C compiler! This is the authentic information I got from the man pages of our Unix-V7 on our university PDP 11.

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But the postings go on to say: He's not sure if it was ever actually called cc in UNIX, but he is _certain_ that the name dd comes from the jcl dd command (so does the wreched syntax). – Justin Ethier Feb 3 '11 at 15:41
This is proving quite an investigation. 'Copy and Convert' describe's dd's function nicely! Some systems did have cc as the 'C-Compiler', and light-bulb moment: does gcc stand for 'GNU C Compiler'? :-) Interesting. – invert Feb 3 '11 at 21:12
+1 for digging up that interesting page! – invert Feb 3 '11 at 21:18
There is a very simple issue involved here. 'DD' is from IBM's JCL and 'dd' is from UNIX .. one is Upper-case, the other Lower-case where case ma.ttered... IBM didn't really have much to do with UNIX and vice-versa... and DD/dd did different things... So, to me, anything other than this is a possibility – Peter.O Feb 5 '11 at 11:13
@invert gcc stands for GNU Compiler Collection, but knowing GNU and their weird obsession with acronyms, it probably stands for both.. – Braden Best Dec 24 '15 at 22:17

"dump data". JCL is irrelevant.

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I believe you are correct. – Rob Feb 2 '11 at 20:33
Yes this does make sense, functionally, even if the origins say something else. – invert Feb 2 '11 at 20:48
Probaby a backronym. secure.wikimedia.org/wikipedia/en/wiki/Backronym – jsbillings Feb 3 '11 at 3:22
Disk Dump is correct. Back then it was normal to use DD to backup a hard drive partition to tape. Most of the other options were related to things that people wanted to do with tapes, such as convert EBCDIC to ASCII. – Michael Dillon Feb 4 '11 at 2:43
It makes a great deal of sense, and is therefore almost certainly wrong. Lexicography is no task for amateurs. – TRiG Nov 15 '14 at 2:17

My guess: it has something to do with "Direct Disk access". :)

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I would've guessed 'data dump' – invert Feb 2 '11 at 20:45

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