voluble, garrulous
嗹 centers on excessive, flowing talk: being voluble or garrulous, with words pouring out in a continuous stream.
嗹 combines 口 (mouth) with 連, which likely contributes both sound and the idea of continuous flow, suggesting a mouth that runs on without stopping.
A mouth 口 that keeps going like a linked chain 連: words flow out endlessly, making the speaker voluble and garrulous.
For レン, imagine a garrulous person who won't stop talking, and you wish you could lend them a mute button: lend -> レン, but their mouth keeps running.