I want to ask about the origins of the paradigm "unused RAM is wasted RAM". Can it be asked here?
I'd say no, for several reasons:
Asking about the origins of something is not related to solving a problem or conveying knowledge about computers. The actual topic you are asking about is who originated an idea or where did it come from. The fact that the idea itself is related to computers does not change the essence of the subject matter.
The specific idea you asked about seems fairly self-evident and obvious. Maybe it wasn't always obvious, but I think the concept surely predates computing. If you have a capacity in some resource for a certain amount of stuff, and the resource isn't completely utilized, whatever is left over is waste, to some degree, since it isn't able to perform its intended function. For instance, a school bus that isn't full is less efficient than a full school bus for the purpose of delivering school children to their school while spending as little money as possible in doing so. It has to carry around empty seats and the steel floor, etc. supporting them.
It is possible that your question could be marginally acceptable if there were developed to have a practical bent to it. For example, if you explained why you need to know this, and it turns out to be relevant to some particular problem you're having, maybe we can help you with the problem rather than going off on this tangent.
While Super User's purpose is to convey knowledge and solve actual problems (most/all questions on the site should follow one of these two patterns - solve a problem or convey knowledge about computing), computing history is somewhat of a gray area, especially when you're "just curious" about it and are not actually going to do anything meaningful with the answer.
Add to that the fact that your question seems fairly obvious, and I'm not sure anyone would even know where this originated from - it's such a common thing that you could likely trace its origins back to the ancient Romans, or even earlier.