Depicts food or drink filling up a container (皿). Based on the original meaning "overflow", now written as 溢. The meaning later shifted to "increase" and "benefit".
Shuowen Jiezi
《說文》：“益，饒也。从水、皿。皿，益之意也。”
Original meaning
overflow
Components
◎(iconic) — Depicts food or drink filling up its container.
皿(iconic) — Depicts a vessel for holding food or drink.