tedious
諄 centers on speech that is repetitive and tiresome: tedious, long-winded, or nagging. The kun readings reinforce the idea of being overly wordy or persistent in a dull way.
諄 combines 言 (speech) with 享, which likely contributes the sound. The character expresses speech that is repetitive and tiresome, though the exact historical development of 享 in this context is uncertain.
Words (言) that go on and on like a monotonous chant (享) become tedious. Picture someone droning on until everyone is bored.
For シュン, imagine a tedious lecture that makes you want to shun the speaker: shun -> シュン, and the long-winded talk drives you away.