!!! Overview
[{$pagename}] is an [Identifier] for a [session]

There is no formal definition for [{$pagename}] and the contents values are typically opaque to all but the [entity] that issued the [{$pagename}].

[{$pagename}] is only unique for the entity that issued it.

[{$pagename}] in [HTTP] [Cookie] maybe referred to as a [session] [cookie]!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]