This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines 魚 (fish) and 白 (white), but the original semantic or phonetic role of 白 in this character is unclear.
The left side is a fish 魚, and the right side is white 白. Imagine a rare white fish whose name you cannot quite remember, so its meaning remains uncertain.
For ハク, picture a white fish that makes a hacking sound as it jumps out of the water: hack -> ハク, and the white fish leaps.