drumstick, raft
桴 centers on a wooden object used for striking or floating: a drumstick for beating a drum, or a raft made of tied logs.
桴 combines 木 (tree/wood) with 孚, which likely contributes the sound. The character originally referred to a wooden drumstick or a raft, both made from wood.
The left side is wood 木, and the right side 孚 looks like a hand holding a stick over a child. Picture a wooden drumstick striking a drum, or logs tied into a raft.
For フ, imagine a wooden drumstick flying through the air with a whoosh sound: whoosh -> フ, as it hits the drum.