Босиком (bosikom) literally means "barefoot". It’s a simple word that JONY uses to create one of the song's most powerful and heart-wrenching images.
He sings, "Я босиком по стёклам бегал так упрямо" (I ran barefoot on glass so stubbornly). This is a vivid metaphor for enduring immense emotional pain, perfectly capturing the feeling of desperately and stubbornly holding onto a relationship that is only hurting you.
This song is pure late-night (or early-morning) heartbreak. JONY sets a dramatic scene right from the start: it's six in the morning and he's burning a photograph of his ex in the fireplace. The chorus repeats this image, telling us his soul is broken and her promises turned out to be «Пустота» (emptiness).
He describes the pain of the relationship with some intense metaphors, like running «босиком по стёклам» (barefoot on glass) for her. He admits that he kept wishing on falling stars not to lose her, but now he's done. He tells her to leave and finally accepts that he has to let go, even though it feels like torture.