Raja Vidya, the King of Knowledge

The titles are not part of the bagavadgita itself. These titles are added by later generations of scholars. Sometimes a chapter can have different titles according to different scholars. But generally this chapter is called raja vidya, raja guhem. So in that sense, this you, this knowledge, uniquely can free you from suffering. Therefore it is raja vida, the highest of all forms of knowledge. And raja guem, little bit more interesting, the most secret of all knowledge.