Is something like DRY a design pattern, a methodology, or something in between? They do not have specific implementations that could neccessarily be demonstrated(even if you can easily demonstrate a case NOT using something like KISS... see The Daily WTF for a plethora of examples), nor do they fully explain a development process like a methodology generally would. Where does that leave these types of "rule of thumb"'s?
In fact, Wikipedia refers to all of them as principles:
In software engineering, Don't Repeat Yourself (DRY) or Duplication is Evil (DIE) is a principle of software development
KISS is an acronym for the design principle "Keep it simple, Stupid!".
The principles when applied together intends to make it more likely that a programmer will create a system that is easy to maintain and extend over time