This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
黵 combines 黑 (black) with 詹, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side 黑 suggests darkness or blackness, and the right side 詹 looks like a complex container. Imagine a dark, mysterious container whose contents are unknown, reflecting the kanji's uncertain meaning.
For タン, picture a dark tan-colored stain spreading across the container: tan -> タン, and the blackness 黑 spreads over the right side.