In a hasty or hurried manner; with haste and lack of careful consideration.
From 'hasty' + suffix '-fly' (variant of '-ly'). The '-fly' suffix is an archaic or dialectal variant of the modern adverb-forming '-ly,' from Old English.
The suffix '-ly' for forming adverbs comes from Old English 'lic' (meaning 'like' or 'body')—so 'hastily' literally meant 'in a hasty manner' or 'in a hasty-like way,' which is why it evolved into our adverb marker.
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