speech leaf

"Speech leaf" is the Japanese word for "word". {言|こと}{葉|ば} kotoba is how you read it. I always thought that "speech leaf" was a really funny way of saying "word", but really, if you think about it, in English we draw "parse trees" for sentences — so it only makes sense that at the end of a branch on a parse tree you would find a "speech leaf", i.e. an individual word.

Naturally, {言|こと}{葉|ば} kotoba is not actually the Japanese word for "word" because of an allusion to parse trees, rather the use of the leaf character is just a phonetic respelling. But it's still an interesting coincidence!

before

The word you read as "before" is お{前|まえ} omae, which is one of the Japanese words for "you". That お o- at the start is a hiragana spelling of {御|お} o-, which is an honorific prefix, so together お{前|まえ} omae means something to the effect of "the honorable presence before me", so that's how you get to the meaning of "you" — the person you're speaking to, who you're in all likelihood facing.

My impression is that お{前|まえ} omae was originally used to politely refer to a highly respected person of a higher social status, but the connotations have shifted so much that Japanese learners are now warned to just stay away from using お{前|まえ} omae to refer to people, because お{前|まえ} omae can come across as very impolite in many situations — hence why it's being used in this hate mail.

The exact level of impoliteness, or the general nuance of the word, does vary depending on dialect, formality, social status, speaker's gender, and things like that, however, so there are some times when you can call people お{前|まえ} omae and it won't be a particularly big deal.