branch, fork, tray
棜 is a rare kanji whose given meanings—branch, fork, tray—do not share one clear conceptual center. It likely refers to a forked branch used as a tray or a tray with a branching shape.
棜 combines 木 (tree/wood) with 於, which may contribute a phonetic element. The exact historical development is uncertain, and the connection between the components and the meanings 'branch', 'fork', 'tray' is unclear.
Picture a wooden (木) tray made from a forked branch. The right side 於 looks like a tray with a handle, and the left side 木 shows it is made of wood.
For ヨ, imagine a yo-yo resting on a wooden tray: yo -> ヨ, and the tray holds the yo-yo.