borrowed from New Latin panacēa "universal remedy, cure-all," going back to Latin, "any of various medicinal plants," borrowed from Greek panákeia "name of a medicinal plant, universal remedy, (as a personified abstraction) a goddess of healing," derivative of panakḗs "all-healing," from pan- pan- + -akēs, adjective derivative of ákos (neuter s-stem) "cure, remedy, relief," of uncertain origin

Note: If initial aspiration was lost, and the aspiration was the residue of yod, then ákos might be comparable with Old Irish ícc "payment, compensation, redemption, act of curing, healing" (Modern Irish íoc), Middle Welsh yach "healthy" (Modern Welsh iach), Old Cornish iach (glossing Latin sānus), Old Breton iac (glossing Latin suspite = sospite "safe and sound") (Modern Breton yac'h "healthy"). The phonetic details are problematic, however.