Lying to students
The concept of lies-to-children, referring to a simplified explanation of a complex topic that the explainer knows isn't strictly true but intends to augment later on, i. e. an intentional untruth intended to help with the learning process, is often said to have coined by the Science of Discworld authors - Wikipedia certainly makes this claim, writing that "[t]he "lie-to-children" concept was first discussed by scientist Jack Cohen and mathematician Ian Stewart in the 1994 book 'The Collapse of Chaos: Discovering Simplicity in a Complex World'", but unsurprisingly it's actually a lot older than that. Here's an earlier example I came across, from Donald Knuth's TeXbook:
Another somewhat unique characteristic of this manual is that it doesn't always tell the truth. When informally introducing certain TeX concepts, general rules will be stated, but later you will find that they aren't strictly true. The author feels that this technique of deliberate lying will actually make it easier for you to learn the concepts; once you learn a simple but false rule, it will not be hard to supplement that rule with its exceptions.
Definitely agree with Knuth there, and on a side note this serves as a good reminder that you cannot trust that Wikipedia will provide accurate, unbiased information. (Unbiased as in not biased towards, among many other things, the present, anglophone nations, and things that nerds are into.)