Making something sour, bitter, or harsh; worsening the severity or harshness of something.
From Latin 'acerbus' (sour, bitter) + '-ate' (verb suffix). The word evolved from describing physical sourness to metaphorical sharpness of tone or mood.
Interestingly, many words about taste (bitter, sour, sharp) became metaphors for personality traits—we literally borrowed flavor language to describe how people treat each other!
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