Etymology
Advertisement
wag (v.)
early 13c. (intransitive), "waver, vacillate, lack steadfastness," probably from a Scandinavian source (compare Old Norse vagga "a cradle," Danish vugge "rock a cradle," Old Swedish wagga "fluctuate, rock" a cradle), and in part from Old English wagian "move backwards and forwards;" all from Proto-Germanic *wag- (source also of Old High German weggen, Gothic wagjan "to wag"), probably from PIE root *wegh- "to go, move, transport in a vehicle."

Transitive meaning "move (something) back and forth or up and down" is from c. 1300; of dogs and their tails from mid-15c.: "and whanne they [hounds] see the hure maystre they wol make him cheere and wagge hur tayles upon him." [Edward, Duke of York, "The Master of Game," 1456]. Related: Wagged; wagging. Wag-at-the-wall (1825) was an old name for a hanging clock with pendulum and weights exposed.
Related entries & more 
Advertisement
wag (n.1)
"person fond of making jokes," 1550s, perhaps a shortening of waghalter "gallows bird," person destined to swing in a noose or halter, applied humorously to mischievous children, from wag (v.) + halter. Or possibly directly from wag (v.); compare wagger "one who stirs up or agitates" (late 14c.).
Related entries & more 
wag (n.2)
"act of wagging," 1580s, from wag (v.).
Related entries & more 
waggle (v.)
late 15c. (implied in waggling), frequentative of wag (v.). Compare Dutch waggelen "to waggle," Old High German wagon "to move, shake," German wackeln "to totter." Transitive sense from 1590s. Related: Waggled.
Related entries & more 
waggish (adj.)
"willing to make a fool of oneself, and fond of doing so to others," 1580s, from wag (n.) + -ish. Related: Waggishly; waggishness.
Related entries & more 
Advertisement
wagtail (n.)

c. 1500, kind of small bird that has its tail in continuous motion (late 12c. as a surname), earlier wagstart (mid-15c.), from wag (v.) + tail (n.). From 18c. as "a harlot," but this sense seems to be implied much earlier:

If therefore thou make not thy mistress a goldfinch, thou mayst chance to find her a wagtaile. [Lyly, "Midas," 1592]
Related entries & more 
*wegh- 

Proto-Indo-European root meaning "to go, move, transport in a vehicle."

The root wegh-, "to convey, especially by wheeled vehicle," is found in virtually every branch of Indo-European, including now Anatolian. The root, as well as other widely represented roots such as aks- and nobh-, attests to the presence of the wheel — and vehicles using it — at the time Proto-Indo-European was spoken. [Watkins, p. 96]

It forms all or part of: always; away; convection; convey; convex; convoy; deviate; devious; envoy; evection; earwig; foy; graywacke; impervious; invective; inveigh; invoice; Norway; obviate; obvious; ochlocracy; ogee; pervious; previous; provection; quadrivium; thalweg; trivia; trivial; trivium; vector; vehemence; vehement; vehicle; vex; via; viaduct; viatic; viaticum; vogue; voyage; wacke; wag; waggish; wagon; wain; wall-eyed; wave (n.); way; wee; weigh; weight; wey; wiggle.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit vahati "carries, conveys," vahitram, vahanam "vessel, ship;" Avestan vazaiti "he leads, draws;" Greek okhos "carriage, chariot;" Latin vehere "to carry, convey," vehiculum "carriage, chariot;" Old Church Slavonic vesti "to carry, convey," vozŭ "carriage, chariot;" Russian povozka "small sled;" Lithuanian vežu, vežti "to carry, convey," važis "a small sled;" Old Irish fecht "campaign, journey," fen "carriage, cart;" Welsh gwain "carriage, cart;" Old English wegan "to carry;" Old Norse vegr, Old High German weg "way;" Middle Dutch wagen "wagon."

Related entries & more 
blather (v.)
1520s, blether, Scottish, probably from a Scandinavian source such as Old Norse blaðra "mutter, wag the tongue," perhaps of imitative origin, or from Proto-Germanic *blodram "something inflated" (the source of bladder). Related: Blathered; blathering.
Related entries & more 
wheedle (v.)
"to influence by flattery," 1660s, of uncertain origin, perhaps connected with Old English wædlian "to beg," from wædl "poverty" [OED], or borrowed by English soldiers in the Thirty Years' War from German wedeln "wag the tail," hence "fawn, flatter" (compare adulation). Related: Wheedled; wheedling.
Related entries & more 
whisk (v.)
late 15c., "move with a rapid sweeping motion" (intransitive), from a Scandinavian source (compare Danish viske "to wipe, rub, sponge," Norwegian, Swedish viska "wipe," also "wag the tail"), from the source of whisk (n.). Transitive sense is from 1510s; meaning "to brush or sweep (something) lightly over a surface" is from 1620s. Related: Whisked; whisking.
Related entries & more