Generalising a bit more to the OpenVMS device naming scheme...
it's usually written as:
ddcu
where "dd" is the device type prefix. 2 letters and registered with a central naming authority. Disk devices usually start with "D". There are many different prefixes. I can say for certain that all of DA, DB, DF, DG, DI, DJ, DK, DL, DP, DQ, DR, DS DU and DV have been used at some time.
They are not acronyms as such, just a code used by drivers to identify different disk types & controler technologies.
The next letter "c" is the controller "A" to "Z", allocated sequentially as the system finds them. Finally the unit number "u", generally 0 through 9999, but some devices have extended the range.
You'll find other device names, and classes of device name. For example those starting with "E" are generally ethernet devices EI, ES, EW, EX,... There are also mailboxes starting with "MB", terminals TN, TT, TX and tape devices MD, MK, MU (I think it's "M" for "Magnetic Tape").
Although the naming scheme is *reasonably* consistent, there are always exceptions to any rule you can glean from looking at SHOW DEVICE. Don't try to read too much into it. A good place to find out about devices is the documentation for the $GETDVI system service.
A crucible of informative mistakes
