Public domain works are free from copyright restrictions. This means that the work can be used by the public in any way and has no attribution requirement.
Through Creative Commons, a work can be placed into the public domain through the “No Rights Reserved” (CC0) license. This license is used by copyright holders who wish to release a work from copyright restrictions. For WordPress, this will typically be the most appropriate license for placing content in the public domain.
It should be added that there is another Public Domain license that Creative Commons offers. This is known as “No Known Copyright,” or public domain mark. This license should not be used by creators who wish to release their own works from copyright restrictions. For that purpose, use the CC0 license.
Adding a “CC0” License to WordPress
To use the “No Rights Reserved” (CC0) license, navigate to the Creative Commons Public Domain page. Under the “CC0” heading, select “use this tool.” This will bring you to a form that will generate code for your WordPress site.