Name of section dedicated for explaining subjects that are not 100% related to main subject of thesis
If it helps the reader understand your process or your findings then the material should remain. That being said, an extra five pages of material not clearly related to your central concept may be distracting. Placing this material in its own appendix section sounds like a great idea though you do risk having the reader not realize it exists. So, for the sake of overall clarity, introduce the additional material briefly in your introduction or background sections - perhaps for a paragraph at most - then refer to the appendix section for the remaining details.