In a way that is shameful, regrettable, or worthy of strong disapproval.
From deplorable + -ly (Old English suffix converting adjectives to adverbs). The root remains Latin deplorare, meaning to express strong sorrow or regret.
Adding -ly to an adjective is so automatic in English that we barely notice it, but it's one of the most productive word-formation patterns in the language, turning virtually any quality word into a manner descriptor.
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