mid-14c., "affording mental or spiritual comfort," from Anglo-French and Old French confortable "comforting; pleasant, agreeable," from conforter "to comfort, solace" (see comfort (v.)); also see -able. Meaning "cheering, cheerful" is from c. 1400. Meaning "offering physical comfort" is attested from 1769; that of "in a state of tranquil enjoyment" is from 1770.
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Definitions of comfy from WordNet
providing or experiencing physical well-being or relief (`comfy' is informal);