moulds on liquids, scum
醭 centers on unwanted growth on the surface of liquids: mold or scum that forms when something ferments or spoils.
醭 combines 酉 (liquor, fermentation) with 菐, which likely contributes the sound. The character refers to mold or scum that forms on fermenting liquids.
The left side 酉 is a jar of fermenting liquid, and the right side 菐 looks like a messy growth spreading on top. Together they show mold or scum forming on the surface.
For ホク, imagine a hawk (ホーク) circling above a vat of fermenting liquid, spotting the scum on the surface: hawk -> ホク.