A yet stronger power than that of herb or stone lies in the spoken word, and all nations use it both for blessing and cursing. But these, to be effective, must be choice, well knit, rhythmic words (verba concepta), must have lilt and tune; hence all that is strong in the speech wielded by priest, physician, magician, is allied to the forms of poetry. [Jacob Grimm, "Teutonic Mythology" (transl. Stallybrass), 1883]Sense of "pleasing quality" evolved 17c. Meaning "small trinket fastened to a watch-chain, etc." first recorded 1865. Quantum physics sense is from 1964. To work like a charm (figuratively) is recorded by 1824.