Middle English quaken, from Old English cwacian "quake (of the earth), tremble, shudder (of persons, from cold, emotion, fear, fever, etc.), chatter (of teeth)," related to cweccan "to shake, swing, move, vibrate," words of unknown origin with no certain cognates outside English. Perhaps somehow imitative (compare quag, quaver, quiver (v.), Middle English quaven "tremble, shake, palpitate," c. 1200). Related: Quaked; quaking. In Middle English formerly also with strong past-participle form quoke. The North American quaking aspen is so called by 1822.
early 14c., "a trembling in fear," from quake (v.). Rare except in combinations, and now usually as a shortening of earthquake, in which use it is attested from 1640s. Old English had the verbal noun cwacung "shaking, trembling." Also compare Middle English quavinge of erþe "an earthquake" (14c.), earthquave (n.), early 15c.
"a member of the Christian denomination known as the Religious Society of Friends," 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 of "one who or that which trembles" is attested from early 15c., an agent noun from quake (v.). The notion of "trembling" in religious awe is in Old English; quaking (n.) meaning "fear and reverence" especially in religion is attested from mid-14c.
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 .... ["A Brief Discovery of a threefold estate of Antichrist Now Extant in the world, etc.," an early Quaker work, London, 1653]
Figuratively, as an adjective, in reference to plain or drab colors (such as were worn by members of the sect) is by 1775. A Quaker gun (1809, American English), originally a log painted black and propped up to resemble the barrel of a cannon to deceive the enemy from a distance, is so called for the sect's noted pacifism. Philadelphia, Pennsylvania, has been known as the Quaker City at least since 1824. Related: Quakerish; Quakeress ("a female Quaker"); Quakerism; Quakerdom; Quakerly.
1610s, from Latin tremulus "shaking, quivering," from tremere "to shake, quake, quiver" (see tremble (v.)). Related: Tremulously; tremulousness.
1640s, "to quake, tremble," phonetic variant of Middle English didderen (late 14c.), which is of uncertain origin. The sense of "vacillate in opinion, be indecisive" is from 1908. Related: Dithered; dithering.
c. 1200, shoderen, "tremble, quake, shiver, vibrate,," not found in Old English; possibly from Middle Dutch schuderen "to shudder," or Middle Low German schoderen, both frequentative forms from Proto-Germanic *skuth- "to shake." Related: Shuddered; shuddering.
c. 1300, "shake from fear, cold, etc.," from Old French trembler "tremble, fear" (11c.), from Vulgar Latin *tremulare (source also of Italian tremolare, Spanish temblar), from Latin tremulus "trembling, shaking, quaking," from tremere "to tremble, shiver, quake," from PIE *trem- "to tremble" (source also of Greek tremein "to shiver, tremble, to quake, to fear," Lithuanian tremiu, tremti "to chase away," Old Church Slavonic treso "to shake," Gothic þramstei "grasshopper"). A native word for this was Old English bifian. Related: Trembled; trembling. The noun is recorded from c. 1600.
"to make a duck sound; utter a harsh, flat, croaking cry," 1610s, earlier quake (late 14c.), variant of quelke (early 14c.), all of echoic origin (compare Middle Dutch quacken, Old Church Slavonic kvakati, Latin coaxare "to croak," Greek koax "the croaking of frogs," Hittite akuwakuwash "frog").
In the same line of Chaucer, various early editions have it as quake, quakke, quak, quat. Frequentative form quackle is attested from 1560s. Middle English on the quakke (14c.) meant "hoarse, croaking." The sense of "talk or advertise noisily and ostentatiously" (1650s) might show influence of quack (n.1). Related: Quacked; quacking.
"to shake, tremble," 1610s, perhaps a variant of dadder, from Middle English daderen "to quake, tremble" (mid-14c.) a frequentative formation on a pattern similar to totter, patter, etc. Wedgwood points to a large group of similar words signifying motion to and fro, including dither, diddle, dandle, toddle, doddle ("shake the head," 1650s). Related: Doddered; doddering.