This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The character visually combines 若 on top and 䖵 (two insects) on the bottom, but the original semantic or phonetic motivation is unclear.
With 若 (young) above and 䖵 (two insects) below, picture young insects that might sting or cause pain, but the exact meaning is uncertain.
For カク, imagine a kak (cackling) sound made by the two insects under the young leaves: kak -> カク.