Болван translates to "idiot" or "blockhead". It's a strong, somewhat old-fashioned insult that stands out in modern lyrics.
In this song, the artist uses it to describe himself, saying "Я болван ведь я курю лесные камыши" (I'm an idiot because I smoke forest reeds). This self-deprecating humor and the unusual imagery make the word memorable and intriguing, hinting at the song's provocative and unconventional tone.
"Ш" is built on one joke, repeated until it turns into a chant. The narrator opens by calling himself a fool, describes a night he barely remembers, and admits he never asked the woman's name. All he can recall is that it started with the letter Ш. Then comes the punchline the whole track exists for: she was your mother.
The chorus does the rest of the work. It repeats the word "шалава", a harsh slang term for a promiscuous woman, and pins a different detail to it each time round. She loves Xanax. She listens to Nirvana. She is your mom. The details never add up to a story, and they are not meant to. They are there to keep the taunt running.
This is shock humour from the Russian underground scene, much closer to a schoolyard insult than to a song about anyone real. 5mewmet leans on the sound of the words as much as on their meaning, which is why a single letter carries the hook and the chorus keeps landing on the same hard syllables.
One note before you study it. The language is crude from the first line to the last, with sexual slang and drug references throughout. These words genuinely turn up in casual Russian speech, so they are worth recognising, but almost none of them belong in a conversation you care about.