Some directories are easy to understand the meaning
/usr
/bin
...
But for the next ones, I have no idea.
/etc
/opt
opt for optional?
etc for electronic t...... configuration (no idea for t)
I would like to know what these abbreviations mean.
The /usr directory originates in the early days of Unix when Ken Thompson and Dennis Ritchie were using two RK05 disk packs (1.5
megabytes each) to develop Unix on their PDP-11. The first disk pack stored the OS and the second, mounted at /usr, stored the users' home directories. When they ran out of space for the OS on disk pack 1, they replicated the OS directories onto the second disk pack in order to use some of this space, which is where we get things like /usr/bin, /usr/sbin, etc. (See 2 for more.)
Since then people have started using the backronym "Unix System Resources" to refer to the /usr directory, but it has no connection to the history of the directory.
"The "etc" in "/etc/bin" really does stand for "etcetera." In early Unix systems, the most important directory was the "bin" directory (short for "binaries" -- compiled programs), and "etc" was for trivial stuff like startup, shutdown and admin. The list of things you need for running Linux is: a program binary, etcetera, etcetera -- in other words, a sole vital item, plus some less important bits and pieces.
Today, "etc" holds system-wide configuration files that you'd almost never do without -- hardly unimportant." --http://searchenterpriselinux.techtarget.com/tip/0,289483,sid39_gci1098161,00.html