Meaning absolutely dead on your feet. More than tired, more than exhausted and more than knackered/shattered. Another way of saying (f*cking knackered)
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."