Origins
Few English words carry their Greek weight as visibly as pyre. It comes from πυρά (pyrá), the funeral fire of the Iliad, itself a derivative of πῦρ (pŷr), simply "fire." When English borrowed it in the 1650s — through Latin pyra, the form used by Virgil and Ovid — it took on the solemnity of the scenes it named: Patroclus laid on his pyre by a grieving Achilles in Iliad XXIII, Hector's pyre burning for twelve days outside Troy in Iliad XXIV, Dido's pyre on the Carthaginian shore in Aeneid IV, Misenus's on the Tyrrhenian in Aeneid VI. The word entered English already soaked in two thousand years of literary grief, and it has never quite shaken off that register.
The Greek root pŷr reconstructs to Proto-Indo-European *péh₂wr̥, one of the oldest nouns in the family and one of the relatively few belonging to the archaic heteroclitic class — a noun whose stem changed between cases (*péh₂wr̥ in the nominative, *ph₂un- in the oblique), a pattern preserved only in the most ancient Indo-European languages. The same root produced Hittite paḫḫur ("fire"), Tocharian A por, Tocharian B puwar, Armenian hur, Umbrian pir, Czech pýř ("hot embers"), and — along a separate Germanic path — Old English fȳr, our modern fire. Pyre and fire are therefore doublets: one word that travelled two routes from the same source and met again in English four millennia later. The Germanic branch underwent Grimm's Law, shifting the initial p- to f-; the Greek branch kept the p-. Had Grimm's Law not operated, English might now speak of striking a pyrestone to light a pyre instead of a firestone to light a fire.
The Indo-European distinction between "fire as substance" and "fire as animate force" is visible in the vocabulary. *péh₂wr̥ was the inanimate noun — the stuff, the thing you could tend, the heat in the hearth. The animate counterpart was *h₁n̥gʷnis, preserved in Latin ignis (whence ignite, igneous, ignition), Sanskrit agní (the Vedic fire god), Lithuanian ugnis, and Old Church Slavonic ognjĭ. Most Indo-European languages retained one of the two; Greek and Germanic kept the first, Italic and Indo-Iranian and Balto-Slavic the second. English absorbed both through borrowing — fire and pyre from *péh₂wr̥, ignite and igneous from *h₁n̥gʷnis — and so carries both ancient nouns in its modern vocabulary without most speakers noticing.
Latin Roots
The Greek branch gave English a whole vocabulary of fire-words. Pyromania (fire-madness) is a nineteenth-century coinage, first recorded in French in 1833 and in English by 1840. Pyrotechnic (fire-art), from the Greek root plus tekhnē ("craft"), entered English in 1729 as a noun for a maker of fireworks, and as an adjective by the 1770s. Pyrexia (fever) is a medical Greek coinage of 1785. Empyrean (the highest heaven, realm of pure fire) is a mediaeval astronomical term, from Greek empýrios — Dante's Empyreo in the Paradiso names the outermost sphere of the cosmos, the abode of God, which he describes as "pure light, intellectual light." Pyrite — the fire-stone that throws sparks when struck with steel — was named in Greek antiquity and passed through Latin into seventeenth-century English mineralogy; the property that gave it its name kept flint-and-pyrite lighters useful for centuries before matches replaced them. Other Greek-root fire-words include pyroclastic (broken by fire, applied to volcanic material), pyromancy (divination by fire), pyrolysis (decomposition by heat), and the element Pyrrhic — which, confusingly, derives separately from the proper name Pyrrhos (meaning "fiery-haired"), the Epirote king whose costly victories gave English "Pyrrhic victory."
Literary attestations of pyre in English begin in the seventeenth century. John Dryden uses it in his translation of Virgil (1697). Pope uses it in his Iliad (1715–20), where the funeral of Patroclus and the return of Hector's body are the most elaborate set-pieces. It appears in Milton's Samson Agonistes (1671) and throughout the Romantic poets — Shelley, Keats, and Byron all reach for pyre when a merely physical fire would not do. The OED's first fascicle (1884) treats it as a fully naturalised English word, distinguishing it from "pile" (a heap of combustible material) by its specifically funerary association.
Pyres themselves predate the word by millennia. The Iliad's funeral scenes, composed around the eighth century BCE but describing Bronze Age practice, are the oldest literary record, but cremation on wooden structures is archaeologically attested across the Indo-European world from at least 2000 BCE. Hindu antyeṣṭi rites, still practised at Manikarnika Ghat in Varanasi and other cremation grounds along the Ganges, follow a Vedic prescription that would have been recognisable to a Mycenaean Greek. Norse ship burnings, recorded by the tenth-century Arab traveller Ibn Fadlan in his eyewitness account of a Rus chieftain's funeral on the Volga, combine pyre with vessel. Roman rogus, Celtic beltaine fires, and the royal pyres of Indian maharajas all describe the same fundamental act: returning the body to fire, which the Indo-Europeans and many other cultures seem to have felt was the proper end of a proper life. The word is ancient because the rite is ancient.