Somebody says
something profound. So you want to acknowledge the person is speaking with solid
knowledge. You don't want to say
Knowledge as that is too verbose. So you respond with "KNOW" - said with inflection similar to "Duude". Saying "Know" to somebodies great idea is an excellent way to show you have carefully studied their idea and in a very positive way have give them kudos for their idea.
Not to be confused with "No" which is just you being disagreeable. This is why the inflection is important. Use it with people in the know. Be Positive!
Similar legacy terms: "Word", "Bet", "No Cap"