Past tense of 'hearken': listened attentively or paid close attention to someone or something.
From Old English heorcnian (hark) with the suffix '-en' added. 'Hearken' is a variant intensification of 'hark,' and both trace to Germanic roots meaning 'to listen,' making 'harkened' the past tense of this more formal version.
English gave us two versions of the same verb—'hark' and 'hearken'—and then both got frozen in time, mostly appearing in Biblical and Shakespearean contexts now.
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