This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The historical origin of 菐 is uncertain. It appears as a component in other characters, but its independent development is not well documented.
The character has no clear meaning, so a mnemonic is not possible. Focus on its shape: top 业, middle 䒑, bottom 夫.
For ホク, imagine a hawk (ホク) perched on the top component 业, but since the meaning is unclear, just remember the sound.