mutter
諵 centers on low, indistinct speech: muttering or murmuring under one's breath.
諵 combines 言 (speech) with 南, which likely provides the sound. The character is used for muttering or murmuring speech.
The speech radical 言 beside 南 suggests words spoken in a low, southern direction—like muttering quietly to oneself.
For ナン, imagine someone muttering 'nan' (like 'nonsense') under their breath: nan -> ナン, and the speech radical 言 reinforces the muttering.
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