The Robert C. Martin Clean Code Collection (Collection)

nowadays HN and other forms of type encoding are simply impediments. They make it harder to change the name or type of a variable, function, or class. They make it harder to read the code. And they create the possibility that the encoding system will mislead the reader.

PhoneNumber phoneString;
// name not changed when type changed!

length of a name should correspond to the size of its scope [N5]. If a variable or constant might be seen or used in multiple places in a body of code, it is imperative to give it a search-friendly name.

Likewise, the name e is a poor choice for any variable for which a programmer might need to search. It is the most common letter in the English language and likely to show up in every passage of text in every program. In this regard, longer names trump shorter names, and any searchable name trumps a constant in code.