In a rough, unrefined, or basic manner; without polish or sophistication; or in a rude or offensive way.
From Latin 'crudus' meaning raw or unripe, related to 'crude.' The adverbial form '-ly' was added in Old English. The metaphorical sense of 'unrefined' developed from the literal sense of raw or unprocessed.
The word 'crude' originally meant literally raw—crude oil is oil before refining, crude rubber before processing—so 'crudely' carries the sense of something needing work, which is why we use it both for unfinished work and for rude behavior that's socially unrefined.
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