Present participle of 'hearken': the act of listening attentively or paying close attention to something.
From 'hearken' plus the gerund/participle suffix '-ing.' The '-ing' suffix creates the continuous form of the verb, allowing it to function as a noun or adjective in various contexts.
'Harkening back' is actually having a small comeback—when someone says 'this harkens back to the 1970s,' the word suddenly makes sense to modern ears as a way to connect past and present.
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