This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
黭 combines 黑 (black) with 弇, which likely contributes the sound. The exact historical development is uncertain.
The left side 黑 suggests darkness or blackness. The right side 弇 looks like a cover over something, so imagine a deep, dark covering that obscures meaning—fitting for a kanji with no clear definition.
For エン, picture an enigmatic dark shape under the cover: enigma -> エン, and the darkness hides its meaning.