This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
胒 combines the flesh component ⺼ with 尼, which likely contributes a phonetic element. The exact historical development and original meaning are uncertain.
The left side ⺼ suggests flesh or body, and the right side 尼 looks like a person sitting. Without a known meaning, picture a body part or flesh-related idea, but treat it as uncertain.
For デイ, imagine a day when you try to guess the meaning of this mysterious flesh-related kanji: day -> デイ.