Literal expression means to tear someone a new butt-hole, figuratively means to verbally or physical abuse or criticize someone thoroughly so that they feel destroyed.
I made a joke about her butt looking big, and she ripped me a new one.
A small piece of information. Derived from the word ken, used often in the scottish language and is synonymous with knowledge.
Person 1: "Hey I don't get this shit. How do you solve this problem?"
Person 2: "I got that one. Give me some kenlets on this assignment and I'll help you w/ that one."