A tool, then a prod at the will
In current English, goad still names a long pointed stick used to drive cattle, but few speakers meet that object outside a farm museum or a footnote. What they meet is the transferred sense: a goad is a pressure that urges someone on, and to goad someone is to incite, provoke, or drive them, often against their inclination. Dictionaries still keep the literal noun and the farm verb, yet the living center of the word is the figurative pair. The history runs in that same direction. English started with a sharp physical object and only later, in the early modern period, made a habit of using the object as a figure for human prompting.
Inherited, not borrowed
The origin of the word goad is native. It was not taken from French or from Latin in the centuries after the Conquest. Old English already had the feminine noun gād, in use before 1150. Early glosses set it against Latin cuspis, a point or spear-head, and against stimulus, a prick used on draught animals. The range is wider than the modern farm tool. A gād could be the tip of a spear or arrow, a sting, or the cattle-prod itself. Ælfric's Colloquy, a classroom dialogue from about the year 1000, puts the word in a ploughman's mouth: the tiller has no goad except by his own skill. The same noun appears in Old English preaching when the biblical ox that kicks back against the prod is translated, so the agricultural sense was already available for moral illustration.
Middle English carried the word as gode, with later spellings such as goode, goude, and gwode. The modern oa spelling is the ordinary development of Old English long ā in this environment, the change that also gives stone from stān and home from hām. There is no extra prefix or suffix to unpack. The noun is a simple inherited stem. The verb is later and clearly denominal: English made a verb out of the noun, not the reverse.
The Germanic circle, and a looser Indo-European one
The immediate ancestor is reconstructed Proto-Germanic *gaidō, a feminine noun for a goad or spear. The firmest outside cognate is Langobardic gaida, attested as spear. North Germanic evidence is a step to the side: Old Norse gedda is the pike, the fish named for a spear-like snout, and Danish gedde and Swedish gädda keep that fish. Scots preserves gad, gade, and gaid beside the southern form. Taken together, the Germanic set points to a word for a point that could be a weapon, a prod, or, by metaphor inside Norse, a fish.
Beyond Germanic the trail is marked as uncertain in the better dictionaries. A proposed Proto-Indo-European root *ǵʰey- gathers verbs and nouns of driving, hurling, and wounding. Sanskrit hinoti and hinvati, to urge on or throw, and heti, a missile, are the usual exhibits. Avestan zaena- for a weapon, Old Irish gae or gath for a spear, and, more tentatively, Greek khaios for a shepherd's staff, are sometimes added. Standard American dictionaries will say the English noun is akin to the Langobardic spear-word and only perhaps to the Sanskrit verb of urging. That hedge should stand. The inner Germanic match is solid; the deep root is a working hypothesis.
A second dispute sits closer to home. English gad, a spike or ox-goad from about 1300, comes from Old Norse gaddr and belongs with Gothic gazds, a sting or prick, and with yard in its old sense of rod. Some older Anglo-Saxon dictionaries lined Old English gād up with that spike-family. Modern notes more often keep the two English nouns apart: similar tools, similar letters on the page, and likely some blending of sense, but not one and the same Germanic word. Folk grouping is easy here and not reliable.
When the stick became a motive
For most of the medieval period the English word stays with the object. The figurative noun, anything that urges or stimulates, is dated to the sixteenth century. The verb is first recorded in the 1570s, and those early uses are already figurative: to incite, stimulate, instigate. Only around the 1610s is the verb attested in the literal sense of driving an animal with the stick. Speakers did not finish a chapter on husbandry and then invent a metaphor. They used the metaphor first, at least in the surviving record of the verb, and the physical sense tagged along.
Biblical English is the likeliest reason the figure felt ready-made. In Acts, the risen Christ tells Saul that it is hard to kick against the ox-goad: the stubborn beast only drives the point deeper. The image is older than the New Testament. Greek tragedy and Latin comedy already used kicking against the goad as a proverb for futile resistance. Old English homilies had already rendered it with gād. Sixteenth-century Bibles put the picture back into wide circulation, sometimes with prick, sometimes with goad. By the time the English verb appears, a literate audience had a shared scene of unwilling motion under a sharp prompt. That is why the modern verb still leans toward unwilling action. Incentive offers a reward. A goad keeps you moving whether you wish to or not, and one dictionary line still glosses the noun as a thorn as well as a spur.
A handful of compounds never left the barnyard: oxgoad, goadman, goadster, goad stick. They show that the literal tool remained nameable while public prose took up the figure.
The pike in the next language
The cleanest fossil is not a sermon but a fish. Scandinavian speakers took the old spear-word and used it for the pike. English kept the pointed staff, then, in the sixteenth century, turned it on the human will. The object is still in the glossary. The verb is what most of us now mean.