How to pick bad function and variable names

I teach a lot of beginner-targeted programming courses, and something that I've experimented with recently is trying to introduce the idea of self-documenting code early on in the learning process. I usually start off by talking about the difference between good and bad names for things (mostly functions and variables, though many of the same arguments apply to class names) , and I've noticed a few common patterns that tend to crop up in beginners code. I thought it might be useful to lay out these common errors in one place.

Single-letter names

OK, we're writing a program ...

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