Diceware is "a better way to create a strong, yet easy to remember passphrase for use with encryption and security programs".
This POSIX shell script is an easy way to get a robot to do the looking up and compiling for you--all you have to do is roll the die and enter your results.
Clone or download this repo, then execute diceware.sh.
cf. https://en.wikipedia.org/wiki/Diceware, http://world.std.com/~reinhold/diceware.html for more on diceware
dictionary.txt created from http://world.std.com/~reinhold/diceware.wordlist.asc