Origins
The Latin word 'corpus' — meaning 'body' — gave English one of its most distinctive word families: a set of borrowings that arrived at different times and through different channels, each preserving a different shade of the original Latin meaning. The triplet 'corpse,' 'corps,' and 'corpus' illustrates how a single source word can yield multiple English forms, each specialized to a different domain.
Corpus traces to the Proto-Indo-European root *kʷrep-, meaning 'body' or 'form.' The PIE labiovelar *kʷ became plain k in Italic, giving Proto-Italic *korpos and then Latin corpus. The root is less well attested outside Italic than many PIE roots, but possible cognates include Old English hrīf ('belly, womb,' surviving dialectally as 'midriff') and Middle High German href ('body').
In Classical Latin, corpus was a third-declension neuter noun with the oblique stem corpor-. Its semantic range was vast. It meant the physical body of a living person or animal, a dead body (a corpse), the trunk as distinguished from the limbs, any physical substance or material, the 'body' of a state or community (corpus reī pūblicae), and a collection of writings (corpus iūris, 'body of law'). This last sense — a unified collection — survives directly in English: a 'corpus' in linguistics is a body of texts; in law, a 'corpus' is a body of evidence; 'Corpus Christi' ('the body of Christ') names both a feast day and a city in Texas.
Middle English
The earliest English borrowing was 'corpse.' Old French reduced Latin corpus to cors (the p and u vanishing in spoken Vulgar Latin), and this entered Middle English around 1225, initially meaning simply 'body' — living or dead. Over the following centuries, the word narrowed to mean exclusively a dead body, a semantic shift completed by around 1600. The spelling 'corpse' (with the p restored by learned influence from Latin) became standard in the seventeenth century.
'Corps' represents a second, later borrowing from French, adopted into English military vocabulary in the early eighteenth century to mean a body of troops — a division of an army. The French pronunciation was preserved: the final ps is silent, giving /kɔːr/. English speakers who pronounce the p are unknowingly reverting to the Latin original.
'Corpus' itself was borrowed directly from Latin in the fifteenth century for learned and legal uses. The legal writ of 'habeas corpus' — Latin for 'you shall have the body' — has been a cornerstone of English-speaking legal systems since the Magna Carta era. Its principle is simple and profound: no person may be imprisoned without being brought physically before a court. The 'body' here is literal: produce the body of the prisoner.
French Influence
The oblique stem corpor- generated the bulk of the derived vocabulary. 'Corporal' (of the body) came through Old French from Latin corporālis. Corporal punishment is punishment of the body. A corporal in the military, however, is an unrelated word — from Italian caporale, from capo ('head'), from Latin caput. 'Corporeal' (having a body, material) came from Latin corporeus. 'Corporate' (formed into a body, united) came from Latin corporātus, the past participle of corporāre ('to form into a body'). A 'corporation' is thus, etymologically, a group of people formed into a single body — a legal fiction that remains the foundation of business law. 'Incorporate' (to embody, to combine into one body) extends this further.
'Corpulent' (having a large body, fleshy) came from Latin corpulentus. 'Corpuscle' (a little body) came from Latin corpusculum, the diminutive — used in science for blood cells and subatomic particles.
Through Old French, corpus also produced 'corsage' (originally the bodice of a dress, the part covering the torso, later a bouquet worn on the bodice), 'corset' (a diminutive of cors, a 'little body,' a garment that shapes the body), and 'corsair' (from Italian corsaro, from Medieval Latin cursārius, 'one who makes a course/raid' — here the connection to corpus is indirect, through the Provençal cors meaning 'course, raid,' though the etymology is debated).
Latin Roots
The philosophical and theological weight of corpus in Western history is immense. The Christian doctrine of the Eucharist centers on corpus Christi — the body of Christ. The political metaphor of the 'body politic,' in which a state is imagined as a human body with the king as its head, derives from Latin corpus reī pūblicae and shaped European political thought for centuries. The legal concept of habeas corpus enshrined the sanctity of the physical body against arbitrary state power. From anatomy to law to theology to business, the Latin word for body remains embedded in the structures of English-speaking civilization.