Shirithian is both an adjective and a noun.
In adjectival use, it means of or pertaining to Shireroth. For instance, "The Shirithian EzBoard" refers to the ezBoard Shireroth maintains.
As a noun, it references the people who are citizens of Shireroth, the Shirithians.
Shirithian, Shirerithian, or Shirerothian?
The Founder of Shireroth, Erik Mortis, is the person who originally coined the term "Shirithian." However, many people disagree with the word, saying that it does not logically or morphologically follow from the word "Shireroth."
There is some confusion as to whether this word is "Shirithian" or "Shirerithian" with the extra syllable. They are used interchangeably by...people of Shireroth...who have developed different habits.
Gryphon Avocatio was the first proponent of using the word "Shirerothian" instead, feeling it made more sense. Since then, many other people have started using the word, including those that had not heard either before.
Other spellings have been suggested, but these three are the most prominent. None is considered to be official; rather, all are considered to be correct.