In a barbarous, crude, or uncivilized manner; with savagery or lack of refinement.
From 'barbaric' plus the adverbial suffix '-ally,' forming an adverb that describes how something is done in a barbarous way. Standard formation for creating adverbs from adjectives.
When medieval or Victorian writers used 'barbarically,' they were often describing violence or behavior that shocked their sensibilities—but what they called 'barbaric' was often just normal for different cultures!
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