dip, ladle
舀 centers on scooping or dipping a liquid or loose material with a tool: using a ladle to transfer something from one container to another.
舀 combines 爫 (a hand or claw reaching down) with 臼 (a mortar or container), suggesting a hand dipping into a vessel to scoop something out.
The top 爫 is like a hand reaching down, and the bottom 臼 is a deep container. Picture a hand dipping a ladle into a mortar to scoop out liquid.
For ヨウ, imagine a yo-yo dipping into a cup: yo-yo -> ヨウ, and the hand scoops it out like a ladle.