This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
嚧 is a phono-semantic compound with 口 (mouth) on the left and 盧 on the right, which likely provides the sound. The exact historical development is uncertain.
The mouth radical 口 beside the complex 盧 suggests a sound or utterance, but the specific meaning is obscure.
For ロ, imagine a low, rumbling sound coming from the mouth: low -> ロ, as the mouth 口 produces a deep note.