I have read somewhere that there is a whole separate book that explains the nautical terminology used in the books, which was recommended as a reference to keep by ones side whilst reading the books. I wonder if it also applies to porcupine-lay or roving line.

I just ran it past an LLM and it provided a decent explanation. Also see @tclancy's reply to @jvandonsel: https://news.ycombinator.com/item?id=49149969