This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
諰 combines 言 (speech) with 思 (think), suggesting a connection to thought or speech, but the exact historical development is uncertain.
The left side is 言 (words) and the right side is 思 (think). Picture someone thinking carefully before speaking, but remember the actual meaning is unclear.
For シ, imagine a person thinking (思) about what to say (言), and the thought begins with 'sh...' as they hesitate: 'sh' -> シ.