This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鎁 is a phono-semantic compound with 金 (metal) and 耶 (phonetic). The exact historical meaning is uncertain, but it likely referred to a type of metal object or tool.
The left side is metal 金, and the right side 耶 suggests a sound. Picture an ancient metal artifact whose name sounds like ヤ, but its exact purpose is lost to time.
For ヤ, imagine a yak made of metal: yak -> ヤ, and the metal yak stands as a mysterious ancient statue.
—