silkworms
蠶 centers on silkworms, the insects cultivated for silk production.
蠶 combines 䖵 (a pair of insects) with 朁, which likely contributes the sound. The character specifically refers to silkworms, a culturally significant insect.
The bottom 䖵 shows two insects, and the top 朁 looks like a complex shelter. Picture a special house where two silkworms are raised together to spin silk.
For サン, imagine the silkworms basking under the sun (サン) inside their shelter: sun -> サン, and the warmth helps them produce silk.