nerdfont.csv is a generated CSV that includes all of the Nerd Font icons and their description, as found on Nerd Font's Cheat Sheet website.
nerdfont.txt is a more readable version of that file
Put nerdfontmenu in your $PATH or a symlink to it. Ensure that nerdfont.txt is in the same location as the actual nerdfontmenu file. To open the menu run
nerdfontmenu
The selection will be added to the clipboard.