exclamatory final particle, nag
囉 centers on vocal expression: an exclamatory final particle used for emphasis, and the act of nagging or chattering repetitively. Both meanings share the idea of persistent or emphatic speech.
囉 combines 口 (mouth) with 羅, which likely contributes the sound ラ and may also suggest a net-like, repetitive quality to the speech. The exact historical development is uncertain.
A mouth 口 on the left and 羅 on the right, which looks like a net full of threads. Imagine a mouth caught in a net of words, nagging and exclaiming without end.
For ラ, picture someone nagging so much it sounds like a drawn-out 'laaaa' — the nagging mouth 口 keeps going 'la, la, la'.