The word כֵּן is an interesting one in that it has a different meaning (somewhat) in the Bible than it does in Modern Hebrew.  You might know it as the Modern Hebrew word for “yes,” but when it appears in the Tanakh, the meaning is “thus” or “so” (as in “it is so”) as an adverb or “right, honest” as an adjective.

For more advanced students, Balashon (tr. “in the tongue/language”) has a very good article covering both of these meanings and how they likely connect.

http://www.balashon.com/2008/04/ken.html