This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
牞 combines 牜 (cow/ox) and 力 (strength/power), but the exact historical development and original meaning are uncertain. It may have originally referred to a strong ox or ox-like strength, but this is speculative.
The left side 牜 suggests a cow or ox, and the right side 力 means strength. Picture a powerful ox pulling a heavy load, but remember that the actual meaning is unclear.
For キュウ, imagine a strong ox (牜) using its power (力) to pull a heavy cart, and the ox's name is 'Q' (キュー). The sound 'Q' cues キュウ.
—