Quaker

1651, said to have been applied to them in 1650 by Justice Bennett at Derby, from George Fox's admonition to his followers to "tremble at the Word of the Lord;" but the word was used earlier of foreign sects given to fits of shaking during religious fervor, and that is likely the source here. Either way, it never was an official name of the Religious Society of Friends. The word in a literal sense is attested from early 15c., an agent noun from quake (v.).

There is not a word in the Scripture, to put David's condition into rime and meeter: sometimes he quaked and trembled, and lay roaring all the day long, that he watered his bed with his tears: and how can you sing these conditions (but dishonour the Lord) and say all your bones quake, your flesh trembled, and that you water your bed with your tears? when you live in pride and haughtiness, and pleasure, and wantonness;" etc. ["A Brief Discovery of a threefold estate of Antichrist Now Extant in the world, etc.," an early Quaker work, London, 1653]