In a manner that clings closely, sticks persistently, or adheres firmly; with attachment or devotion.
From the archaic verb 'cleave' (to adhere, from Old English 'clifian') plus the adverb suffix '-ly.' This creates an adverb form describing the manner of clinging or sticking.
The adverb 'cleavingly' preserves the archaic 'cleave' meaning and appears in poetry and religious texts—when someone acts 'cleavingly,' they're showing devotion or loyalty by staying as close as possible, literally or figuratively.
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