What speakers mean by it now
A test, in current English, is a trial with a result. Students sit one. Laboratories run one on a sample. Engineers put a beam, a car, or a piece of software through one. The shared idea is simple: expose something to conditions that will show what it is worth, or whether it works. That abstract sense is so ordinary that the older, concrete meaning is easy to miss. For several centuries the noun named a pot.
The origin of the word test is easier to see if you start with that pot, not with the classroom.
A French vessel in Middle English
English borrowed the noun in the late fourteenth century. Middle English has test and teste. The source is Old French and Anglo-French test, a word for a pot, already used for the small vessel in which gold and silver were assayed. Metallurgists still call that object a cupel: a shallow, porous dish. When an alloy is heated in it, base metals oxidize and soak into the clay. What remains is a button of precious metal. The English noun first pointed at that dish, and sometimes at a potsherd. Surviving evidence from around 1386, in Chaucer, already shows the workshop sense. That technical meaning never quite vanished. In British usage, test can still mean the cupel itself, or the iron frame that holds it as the movable hearth of a furnace.
French later specialized the same object as têt. English kept the older spelling and, over time, almost everything except the original job of the vessel.
Latin clay, shells, and an unsettled root
Old French test comes from Latin testum, an earthen pot or the lid of one. Beside it stands testa: a piece of burned clay, a tile, a potsherd, and also a shell. Medieval Latin used the pot word in a narrow workshop sense, for the vessel in which metals were tried. The shell sense is not a side note. Testa is behind Latin testudo, the tortoise, named for its covering. English biology still uses a related form: the hard outer case of a sea urchin is a test, and the coat of a seed is a testa. Spanish tiesto, a flowerpot, keeps the household meaning. Italian and French went another way with testa and turned a skull-like shell into a word for head; French tête is that development.
How far testa and testum go beyond Latin is disputed. Some reference works reconstruct an Indo-European root meaning to weave or to fabricate, as if a vessel were something made. The Latin etymologist Michiel de Vaan, writing in 2008, finds a link to the root for building unlikely on semantic grounds and treats testa as probably a loanword, noting that names for pots often are. Older English dictionaries sometimes grouped the word with dryness and earth, placing it near terra and thirst. Those deeper stories do not agree, and none of them is required to explain the English noun. The path that is firm is shorter: Latin clay vessel, French cupel, Middle English borrowing.
The word is a simplex in English. There is no native prefix or suffix hiding in it. A look-alike family from Latin testis, a witness, produced testify, testimony, and testament. Those words share letters with test and nothing else of its history. Treating an exam as a kind of witness is folk etymology.
From the hearth to the examination
The sense of trial is a metaphor from the workshop. Melt an alloy in a cupel and you learn what the metal really is. By the 1590s English writers were using that picture for any critical examination of quality or truth. Shakespeare still said to bring something to the test. Put to the test became the usual phrasing later, common from the early nineteenth century and recorded from the late eighteenth. By the time of Samuel Johnson's dictionary in 1755, the noun could already mean a means of trial in general, not only a goldsmith's dish.
The verb grew from the noun. Around 1600 it meant to assay gold or silver in the vessel. The figurative use, to put something to the proof, appears by 1748. People undergoing a test, and testers administering one to a person, are twentieth-century developments, from the 1930s. Academic and psychometric tests — a set of questions meant to measure knowledge, skill, or ability, often treated as lighter than an examination — are in place by the early 1900s. Mechanical trials of strength and safety, the ancestors of the crash-test, are recorded by 1877. Test-drive, for an automobile, is mid-twentieth century.
English statute law preserved an older, sterner use. The Test Acts, above all the act of 1673, made oaths of supremacy and the taking of sacraments a condition of public office. The point was to exclude Catholics and many Nonconformists. Here a test was a required proof of belief, not a quiz. The 1673 act was repealed in 1828.
The French loan took over ground that Old English had covered with native words for trial, among them afandung. Whether or not that particular replacement is the whole story, the borrowed pot-word won the later standard language.
A tortoise and a cupel
If one detail is worth keeping, it is how much of the family still means a hard covering. A tortoise is a testudo because of its shell. A sea urchin has a test. A seed has a testa. French tête is a head that began as a potsherd. English took the same Latin clay, kept the assayer's cupel, and then used the fire in that cupel as a picture of proof. Every classroom quiz still carries a faint workshop image: heat the thing, and see what is left.