The speaker confesses to a private obsession: the final word of anything, whether it's a book, a song, a joke, or something a person said to them. Each person in their life gets boiled down to one last word. A best friend becomes "know," a father becomes "grass," a brother becomes "goodnight," and the speaker themselves becomes "star," the last word they spoke aloud. It's a strange, touching way of summing up relationships, as if a whole person could be held in a single leftover sound.
The speaker is a little embarrassed. They call the habit a fetish, something "stupid" and taboo that you don't talk about. Then the tone shifts. Words aren't "just words" but constellations, meaningless letters strung together into infinite meanings. The star image ties it all together. The mood is quiet, confessional, and half-shy, ending with a small, firm claim that the last word is everything, at least to them.