One of the things that helps improve documentation is good variable names. If you are working with financial systems don’t call your variables A, B, and C. Likewise, if you are doing a client service system don’t name your variables carrots, peas, onions and apples. Yes, it makes an interesting recipe, but that’s about all.
I remember once when we had to have some code recreated from source. The generated code was full of variables named A1, A2, A3, …. It was a thorough pain in the neck. In order to make the code usable, maintainable, we had to work through the code and figure out what A1 was, what it did, how it was used, and then give it a useful name, a meaningful name. Then work through A2, then A3, and finally we got to A4178. (Or was that A7841? Whatever, it took a LONG time!) But, when you have a critical system that needs maintenance, you need to do whatever you need to do to keep the business working.
To help you with your variable naming chores, here is this link from Ian Hickman on the 5 rules of variable naming.