mulberry fruit
葚 refers specifically to the fruit of the mulberry tree, a small edible berry.
葚 combines the grass radical 艹 with 甚, which likely contributes the sound. The character is used for mulberry fruit, but the exact historical development is uncertain.
The grass top 艹 suggests a plant, and the bottom 甚 looks like a container full of small round berries. Picture a mulberry bush laden with fruit.
For チン, imagine a chin stained purple from eating too many mulberries: chin -> チン, and the juice drips down your chin.