bamboo skin, bamboo
筠 centers on bamboo, specifically its outer skin or husk, but can also refer to bamboo more generally.
筠 combines 竹 (bamboo) with 均, which likely contributes the sound. The character originally referred to the green outer skin of bamboo.
The bamboo top 竹 sits above 均, like the even, smooth outer skin covering the bamboo stalk. Picture peeling away the green skin to reveal the bamboo inside.
For イン, imagine an inn made entirely of bamboo, with smooth bamboo skin walls: inn -> イン, and the bamboo inn is covered in 筠.