Comfortably

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Middle English (in the sense ‘pleasant, pleasing’): from Anglo-Norman French confortable, from conforter ‘to comfort’ (see comfort).

wiktionary

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comfortable +‎  -ly

etymonline

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comfortably (adv.)

late 14c., "pleasantly, enjoyably," from comfortable + -ly (2). Meaning "in a state of comfort" is 1630s.