(of a horse) lively, vigorous
騤 centers on a horse full of energy and strength: lively, vigorous, and spirited in movement.
騤 combines 馬 (horse) with 癸, which likely contributes the sound. The character is used to describe a horse's lively, vigorous movement.
The left side is a horse 馬, and the right side 癸 looks like a complex, energetic shape. Picture a horse bursting with so much energy that its outline seems to vibrate with extra strokes.
For キ, imagine a lively horse that has found the key to endless energy: key -> キ, and the horse gallops vigorously.