volume, book, part
卷 centers on a rolled-up or bound collection: a volume or part of a book, or a scroll-like unit of writing.
卷 is the older form of 巻. It combines 龹 (a phonetic component) with 㔾 (a kneeling person), suggesting a rolled or bent shape, which extended to scrolls and book volumes.
The top 龹 looks like a rolled scroll, and the bottom 㔾 resembles a person kneeling to read it. Together they make a book volume.
For カン, imagine a can of rolled-up scrolls: can -> カン, and each scroll is a volume of a book.