the word brain is used in its opposites such as to demean and criticize. that is why someone of great stature is called by your head but not by your brain.
والدماغ يستعمل في أضداد ذلك فيستعمل في التحقير والذم. ولذلك يقال للعظيم وحق رأسك ولا يقال وحق دماغك.