play with words, quip, talk nonsense
謅 centers on frivolous or nonsensical speech: playing with words, making quips, or talking nonsense.
謅 combines 言 (speech) with 芻, which likely contributes the sound and may relate to cutting grass, but the exact historical development of the meaning 'play with words' is uncertain.
The left side 言 is speech, and the right side 芻 looks like a bundle of grass being cut. Picture someone cutting words like grass, making playful quips and nonsense talk.
For ソウ, imagine a person sowing nonsense words like seeds: sow -> ソウ, and their speech is just playful quips.