Wholly

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Middle English: probably already in Old English(see whole, -ly2).

wiktionary

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From Middle English holly, holeliche, holliche (also as halely, hallich, etc.), equivalent to whole +‎ -ly.

etymonline

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wholly (adv.)

mid-14c., from whole (adj.) + -ly (2), or a modification of unrecorded Old English *hallice.