This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 夡 is uncertain. It visually combines 多 and 吉, but the original semantic or phonetic role of these components is unclear.
With no clear meaning, picture 多 (many) and 吉 (good fortune) together as a vague idea of abundant good luck, but treat this as a placeholder, not a real definition.
For キ, imagine a key unlocking a mysterious box labeled 夡: key -> キ, but the contents remain unknown.