Highly

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Old English hēalīce (see high, -ly1).

wiktionary

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From Middle English hiȝly, heȝly, heyȝliche, from Old English hēalīce(“highly”), equivalent to high +‎ -ly. Cognate with Dutch hoogelijk(“highly”), German höchlich(“highly”), Danish højlig(“highly”), Swedish högligen(“highly”).

etymonline

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highly (adv.)

Old English healice "nobly, gloriously, honorably;" see high (adj.) + -ly (1). Meaning "very, very much, fully" is mid-14c.