Etymology Dictionary

GAD (1),  a wedge of steel, goad.  (Scand.)   'A gad of steel;' Titus Adnron. iv. I. 103.   Also 'upon the gad,'  i.e. upon the goad, suddenly; K. Lear, i. 2. 26.   'Gadde of steele, quarreau dacier;' Palsgrave.   M. E. gad, a goad or whip; 'bondemen with her gaddes' = husbandmen with their goads or whips; Havelok, 1016.—Icel. gaddr (for gasdr), a goad, spike, sting, cognate with E. goad, yard.   See Goad, Yard.   Der. gad-fly, i.e. sting-fly; and see gad (2).

GAD (2),  to ramble idly.  (Scand.)   'Where have you been gadding?'  Romeo, iv. 2. 16.   'Gadde abrode, vagari;' Levins, 7. 47.   The orig. sense was to drive, or drive about.—Icel. gadda, to goad.—Icel. gaddr, a goad.   See above.   ¶ I see no connection with M. E. gadeling, an associate, for which see Gather [†]

ADDENDA

GAD (2).   Wedgwood explains this by 'to run hither and thither without persistent aim, like cattle terrified by the hum of the gadfly.'   He cites the Ital. assillo, 'a sharpe goade,' Florio; and assillare, 'to bite with a horseflie; also to leap and skip furiously, as oxen do, when they are stung and bitten with flies.'   If this be so, then gad, v. is from gad, sb., just as the Icel. gadda is from gaddr; only it was formed in England.   It makes very little difference to the etymology.   See quotations in Richadson and Johnson.