beams in the roof of a house confused, disordered
棼 centers on tangled disorder, like roof beams that are jumbled and confused. The idea extends to anything messy or disordered.
棼 combines 林 (forest, many trees) with 分 (divide, separate), suggesting tangled or disordered beams. The exact historical development is uncertain, but the component combination plausibly conveys confusion.
A forest (林) of beams divided (分) and jumbled together creates a confused, disordered roof structure.
For フン, imagine the fun of untangling a messy pile of beams: fun -> フン, and the disorder becomes a playful puzzle.