This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鉨 combines 金 (metal) with 尔, but the exact historical development and original meaning are uncertain.
The left side is metal 金, and the right side 尔 looks like a small person or a simplified shape. Without a clear meaning, picture a mysterious metal object with an unknown purpose.
For デイ, imagine a day when you discover a strange metal artifact: day -> デイ, and the metal 金 side hints at the object.