In a harshly sour, bitter, or sharp manner; with cutting or biting tone or criticism.
From 'acerb' (adjective) + '-ly' (adverb suffix). 'Acerb' comes from Latin 'acerbus' (sour, harsh).
Adverbs ending in '-ly' are so common we forget they're magical—they instantly turn any adjective into a description of how something happens!
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