This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form visually combines 臤 and 子, but the original meaning and component function are unclear.
No clear meaning is known, so a mnemonic is not possible.
For カン, imagine a can (カン) with a child (子) sitting on top of a sturdy (かたい) box (臤).