What is signifigance of "rc" and "rd"
 

I see "rc" used in linux as rc.local etc. What does "rc" relate to?
I also se "rd" used as initrd. What does "rd" relate to?
Thanks

rc, probably "runtime configuration" or "resource configuration", just a guess. It's not only used for the init system configuration stuff, but also, under your $HOME there will probably be some dot files that end in "rc", like ~/.bashrc and so on.

rd stands for "ram disk". The initrd image is a file that contains a small filesystem that is loaded into ram when booting, and usually contains drivers are are needed before the kernel can access the disk at a file system level (for example, the file system drivers, which can't be loaded from a file system that's not working yet, because well, the drivers have not been loaded :p you get the idea).

Thanks for the response!
I think I can buy into "rd stands for Ram Disk" but I have my doubts about "rc standing for resource configuration". :-)
Lacking a definitive answer I will go with "Runtime Configuration". Seems pretty close to the action that occurs.
Thanks for the help!