Past tense of hearken; listened attentively or paid close attention in the past.
From 'hearken' (Old English 'heorcnian') with the regular past tense '-ed' suffix, indicating a completed action of attentive listening.
The past tense 'hearkened' appears mainly in historical narratives and scripture—'And he hearkened unto her voice'—where it signals not just listening but obedience and submission, which is why it survives in those registers even as the present tense 'hearken' fades!
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