What is the meaning behind "淵騫"?
They are two famous disciples of Confucius. 淵: 顏淵 (顏回)、騫: 閔子騫 (閔損)。

It is common practice in classical Chinese literature to label chapters in a book by the first word of substance, regardless of whether it actually pertains to the central meaning or not. In this case, the chapter begins with a question on the practices of these two disciples of Confucius, and their names are taken to form the chapter name.