In a babbling manner; while speaking rapidly, incoherently, or excessively without clear meaning.
From 'babble' plus the present participle suffix -ing, then the adverbial suffix -ly. This represents the most common English pattern for creating adverbs from verbs: verb → -ing form → -ly.
English adverb formation is incredibly systematic—once you understand that babble → babbling → babblingly follows the same rule as 'run → running → runningly' (though we'd never use it), you've grasped one of English's most productive patterns.
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