This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
暿 combines 日 (sun) with 喜 (joy), but the exact historical development is uncertain. It may have originally expressed a sense of bright or warm joy, but this is speculative.
The sun 日 beside joy 喜 suggests a bright, happy day, but the actual meaning is unclear.
For キ, imagine a key (キ) unlocking a bright, joyful day: key -> キ, and the sun shines on happiness.