The term 'Hagiography' is derived from the Greek word "hagios," which means "holy" or "saint," and "grapho," which means "to write" or "to describe." Therefore, a hagiography is a type of biography that focuses on the lives and virtues of individuals who are regarded as holy or saintly within a religious context.

The reason 'Hagiography' is specifically associated with the biography of religious leaders or saints is that it is a genre of literature primarily concerned with the religious or spiritual aspects of a person's life, often highlighting their pious and virtuous qualities and any miraculous events associated with them. While other biographies of military or political leaders exist, these are typically referred to by different terms.

So, the correct option is [3].