Back in the late nineties, I worked with a software called Origin. It had a BASIC like programming language where variable names consisted of single letters. If

Back in the late nineties, I worked with a software called Origin. It had a BASIC like programming language where variable names consisted of single letters. If you now think 26 variable names should be enough: Some letters, like X and Y, had special predefined meaning, and you couldn't change that. If you used them, you encountered strange behavior, like values changing behind your back. To add insult to injury I could never find documentation about which variables were special, so I stuck with the few I knew were safe, which were not many...