coughing
謦 centers on the sound or act of coughing, specifically a light cough or clearing of the throat.
謦 combines 殸 (a component associated with sound) and 言 (speech), suggesting a vocal sound like coughing. The exact historical development is uncertain.
The top part 殸 looks like a hanging stone instrument that produces sound, and the bottom 言 is speech. Imagine a speech interrupted by a light cough, the sound echoing like a small chime.
For ケイ, picture a person named Kay clearing her throat with a light cough before speaking: Kay -> ケイ.