Plural of harrow: farming tools with teeth or spikes that break up and level soil, or the verb meaning to distress deeply.
From Old English 'hearwe,' a leveling agricultural implement. The tool sense predates the emotional metaphor by centuries. The verb meaning 'to distress' derives from the destructive aspect of the tool.
A single word with two totally different meanings—one literal (the farming tool) and one metaphorical (to emotionally distress)—shows how English speakers make meaning by comparing emotional pain to physical disruption of the earth!
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