Why is E the most common across multiple languages (except Lisp (which I assume is due to the parentheses))? I assume it's usage is higher because it's a vowel, but none of the other vowels are nearly that high.
I only know about this because it was referenced in a book on cryptanalysis. The simplest sort of cipher can be broken by paying attention to the relative frequency of letters in the original text. I remember a useful mnemonic for remembering the most common letters: the sentence "a sin to err" contains them. E, followed by t and a, are the most common out of those (t and a are very close).
However, it is in most of my variable names. Given that it's the most common letter in English, that makes sense.
There's the famous phrase "ETAOIN SHRDLU", dating back to printing press days, of the approximate order of the most common letters in English.
Not to be confused with the early AI program "SHRDLU"". :-)