O "k" significa é hungarian notation (e segundo alguém no Stack Overflow, [legacy from the pre-Mac OS X days](http://stackoverflow.com/a/1230863/1380781)).
"NC" é também para [const](https://developer.apple.com/library/mac/documentation/cocoa/conceptual/codingguidelines/Articles/NamingIvarsAndTypes.html#//apple_ref/doc/uid/20001284-1003018) e [functions](https://developer.apple.com/library/mac/documentation/cocoa/conceptual/codingguidelines/Articles/NamingFunctions.html#//apple_ref/doc/uid/20001283-BAJGGCAD) segundo os "Coding Guidelines for Cocoa" da Apple.