whirr
翽 centers on the sound of wings beating rapidly, producing a whirring noise. It describes the audible flutter of a bird in flight.
翽 combines 羽 (wings) with a phonetic component that likely contributed the sound. The character is associated with the sound of wings in motion, but the exact historical development of the left component is uncertain.
The right side 羽 shows wings, and the left side 歲 looks like a complex mechanism. Imagine a mechanical bird whose wings beat with a loud whirr.
For カイ, picture a kite (カイト) whose wings whirr as it flies: kite -> カイ, and the sound of the kite's wings matches the whirring.