drum
駴 centers on a drum, specifically a type of drum used in ancient contexts. The meaning is narrow and concrete, with no clear abstract extensions.
駴 combines 馬 (horse) with 戒, which likely contributes the sound. The exact historical development is uncertain, but it may refer to a drum associated with horses or a specific type of drum.
A horse (馬) stands beside a warning (戒) drum. Imagine a horse-drawn cart carrying a large drum used to sound alerts.
For カイ, picture a horse-drawn drum being played at a lively outdoor fair (カイ). The drum beats echo across the fairground.