scream
譆 centers on a loud, sharp vocal outburst: a scream or cry. It is a rare character used for exclamatory or screaming sounds.
譆 combines 言 (speech) with 喜 (joy), suggesting a joyful or loud vocal expression. The exact historical development is uncertain, but the component structure points to a phono-semantic origin where 喜 contributes both sound and the idea of an exclamation.
Words (言) of joy (喜) burst out as a loud scream. Imagine someone so happy they can't help but shriek with delight.
For キ, picture a person screaming 'KEY!' as they joyfully unlock a treasure chest: key -> キ, and the scream fits the meaning.