Old English gad "point, spearhead, arrowhead, pointed stick used for driving cattle," from Proto-Germanic *gaido "goad, spear" (cognates: Lombardic gaida "spear"), from suffixed form of PIE root *ghei- (1) "to propel, prick" (cognates: Sanskrit hetih "missile, projectile," himsati "he injures;" Avestan zaena- "weapon;" Greek khaios "shepherd's staff;" Old English gar "spear;" Old Irish gae "spear"). Figurative use "anything that urges or stimulates" is since 16c., probably from the Bible.

1570s, from goad, n.; earliest use is figurative, "incite, stimulate, instigate." Literal use by 1610s. Related: Goaded; goading.