This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 龏 is uncertain. It visually contains 龍 and 廾, but the original semantic and phonetic roles of these components are unclear.
No clear meaning is known, so a mnemonic cannot be reliably formed. The shape shows a dragon 龍 over two hands 廾, but this does not point to a specific meaning.
For キョウ, imagine a dragon (龍) roaring 'kyou!' as it raises its hands (廾) in a dramatic pose: kyou -> キョウ.