> I couldn't for the life of me tell you what dd stands for.

Data(set) Definition. But that name does not make any sense whatsoever by itself in this context, neither for the tool (it hardly "defines" anything), nor for UNIX in general (there are no "datasets" in UNIX).

Instead, it's specifically a reference to the DD statement in the JCL, the job control language, of many of IBM's mainframe operating systems of yore (let's not get into the specifics of which ones, because that's a whole other can of complexity).

And even then the relation between the DD statement and the dd command in UNIX is rather tenuous. To simplify a lot, DD in JCL does something akin to "opening a file", or rather "describing to the system a file that will later be opened". The UNIX tool dd, on the other hand, was designed to be useful for exchanging files/datasets with mainframes. Of course, that's not at all what it is used for today, and possibly that was true even back then.

This also explains dd's weird syntax, which consists of specifying "key=value" or "key=flag1,flag2,..." parameters. That is entirely alien to UNIX, but is how the DD and other JCL (again, of the right kind) statements work.