There is no facility to provide user written help on a variable, or mouseover capability to do the same.
Perhaps an option is to use structs. Include in each struct a help field, as well as a field that actually contains the information in the variable. Or, you could write your own class to do the same. In any case, these variables will be more cumbersome to work with and use. I seriously doubt it is worth the effort.
As Rik suggested, a good option is to learn to use descriptive variable names. Don't name your variables a,b,c, etc. There is no charge for longer variable names, and a good descriptive name is well worth the effort, in terms of debugging and just ease of use. Tab completion will make things easy.
