bamboo frame on which silkworms spin their cocoons
筁 refers to a specific bamboo frame used in sericulture for silkworms to spin their cocoons.
筁 combines 竹 (bamboo) with 曲 (bend, curve), likely indicating a bent bamboo frame. The exact historical development is uncertain.
Bamboo 竹 bent into a curved 曲 frame for silkworms to spin their cocoons.
For キョク, imagine a silkworm spinning a cocoon on a bamboo frame while listening to a catchy tune: the tune's hook goes 'kyoku' -> キョク.