In a skillful or clever manner; with dexterity or ease.
From Old French habilement, from habile (skillful) plus -ment (the suffix forming adverbs). This French-derived adverb became part of English in formal writing and has remained relatively rare.
French adverbs ending in '-ment' are like English adverbs ending in '-ly'—they transform adjectives into ways of doing things. The fact that 'habilement' exists shows how medieval writers loved building words in elegant, logical ways.
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