This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
謞 combines 言 (speech) with 高 (tall, high), suggesting a meaning related to loud or elevated speech, but the exact historical development is uncertain.
With 言 (speech) and 高 (high), picture someone speaking from a high platform, their voice carrying far. This might suggest loud or elevated speech, but the exact meaning is unclear.
For カク, imagine a loud speaker on a high platform making a sharp 'kak' sound: kak -> カク.