This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
苨 combines the grass radical 艹 with 尼, but the historical origin and original meaning are uncertain.
The grass radical 艹 sits above 尼, but without a clear meaning, picture an obscure plant whose name is lost.
For デイ, imagine a day when you discover a mysterious plant: day -> デイ, and the plant is 苨.