Origins
The word 'subpoena' is another example of a writ named by its opening Latin words β in this case, 'sub poena,' under penalty.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ The writ commanded its recipient to appear in court or produce documents, and it made explicit the consequences of non-compliance: there was a penalty, a punishment, waiting for those who defied it. This bluntness was deliberate. Unlike a simple summons, which invited appearance, a subpoena threatened it, and the penalty for ignoring one β typically contempt of court β gave the writ its coercive force.
The Latin 'sub' (under, beneath) is cognate with Greek 'hypo-' and traces to PIE *upo (up from under, under), a remarkably stable root visible in 'up,' 'over,' 'above,' and in the Greek and Latin prefixes that mean 'under' or 'below.' It contributes to hundreds of English words: 'submarine,' 'suburb,' 'subvert,' 'subject,' 'subordinate,' and many more.
The second element, 'poena,' is the more etymologically fascinating half. Latin 'poena' (punishment, penalty) was a direct borrowing from Greek 'poinΔ,' a word with deep roots in archaic Greek society. 'PoinΔ' originally meant the blood-money paid by a killer's family to the victim's family to settle a feud and avoid retaliatory killing β a payment made to atone for a death. This practice of compensatory payment for injury, older than formal courts, is reflected in the Proto-Indo-European root *kΚ·ey- (to pay, to atone, to compensate for a wrong). The Greek 'poinΔ' was thus at its origin a payment that bought peace, not merely a punishment imposed by a state.
Old English Period
Latin adopted 'poena' and extended it to mean punishment of any kind. From it came 'punire' (to punish), 'poenalis' (relating to punishment, whence 'penal'), and through Old French 'peine' into English as 'pain' β the suffering that punishment inflicts. The English word 'pain' and the English word 'penalty' are thus siblings, both descending from the same Greek 'poinΔ.' 'Impunity' (from Latin 'impunitas,' without penalty) is the same root with a negative prefix. 'Pine' in its sense of suffering or languishing ('to pine for something') comes from Old English 'pΔ«nian,' borrowed from the Latin 'poena' via a very early adoption.
The specific writ 'subpoena ad testificandum' (to compel testimony) and 'subpoena duces tecum' (to compel production of documents β literally 'you shall bring with you') were standard instruments of English common law courts from the fifteenth century onward. The subpoena duces tecum has become particularly important in modern litigation as the primary mechanism for compelling parties and non-parties to produce documents, electronic data, and other evidence. Both forms of subpoena are used in every common-law jurisdiction, and their Latin names remain in active use in courts today, two medieval writs still conducting legal business under their original names.