Old English gad "point, spearhead, arrowhead," from Proto-Germanic *gaido (cf. Lombardic gaida "spear"), from PIE *ghei- (cf. 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 is since 16c., probably from the Bible.