One of Mr. Nunberg's chapters is titled Ten Suffixes That Changed the World (and he only named four of them, dang it!), but my attention has fallen on a prefix.

How did 'un' come to be used for negation? Or, as my Chambers interestingly says, ...more than a mere negation, it has a positive force ..., using the example of unkind meaning "cruel", not just "not kind".