The word originated as a compound of Ancient Greek παν- 'all' (the form taken by the word πᾶν, neuter of πᾶς 'all', when that is used as a prefix) and the word ἄγυρις 'assembly' (an Aeolic dialect form, corresponding to the Attic or Ionic form ἀγορά). Compounded, these gave ancient Greek πανήγυρις 'general or national assembly, especially a festival in honour of a god' and the derived adjective πανηγυρικός 'of or for a public assembly or festival'. In Hellenistic Greek the noun came also to mean 'a festal oration, laudatory speech', and the adjective 'of or relating to a eulogy, flattering'. The noun πανήγυρις had been borrowed into Classical Latin by around the second century CE, as panēgyris 'festival' (in post-Classical usage also 'general assembly'). Correspondingly, Classical Latin also included the adjective panēgyricus, which appears meaning 'laudatory', but also came to function as a noun, meaning 'public eulogy'. These words inspired similar formations in European languages in the early modern period, such as French panégyrique, attested by 1512. The English noun and adjective panegyric seems to have been borrowed from the French word, but no doubt with cognisance of its Latin and Greek origins.
In Athens such speeches were delivered at national festivals or games, with the object of rousing the citizens to emulate the glorious deeds of their ancestors. The most famous are the Olympiacus of Gorgias, the Olympiacus of Lysias, and the Panegyricus and Panathenaicus (neither of them, however, actually delivered) of Isocrates. Funeral orations, such as the famous speech of Pericles in Thucydides, also partook of the nature of panegyrics.
The Romans generally confined the panegyric to the living, and reserved the funeral oration exclusively for the dead. The most celebrated example of a Latin panegyric, however, is that delivered by the younger Pliny (AD 100) in the Senate on the occasion of his assumption of the consulship, which contained a eulogy of Trajan considered fulsome by some scholars.
Towards the end of the 3rd and during the 4th century, as a result of the orientalizing of the Imperial court by Diocletian, it became customary to celebrate as a matter of course the superhuman virtues and achievements of the reigning emperor, in a formally staged literary event. In 336, Eusebius of Caesarea gave a panegyric of Constantine the Great on the 30th year of his reign, in which he broke from tradition by celebrating the piety of the emperor, rather than his secular achievements. A well-delivered, elegant and witty panegyric became a vehicle for an educated but inexperienced young man to attract desirable attention in a competitive sphere. The poet Claudian came to Rome from Alexandria before about 395 and made his first reputation with a panegyric; he became court poet to Stilicho.
Cassiodorus the courtier and magister officiorum of Theodoric the Great and his successors, left a book of panegyrics, the Laudes. One of his biographers, O'Donnell, has described the genre thus: "It was to be expected that the praise contained in the speech would be excessive; the intellectual point of the exercise (and very likely an important criterion in judging it) was to see how excessive the praise could be made while remaining within boundaries of decorum and restraint, how much high praise could be made to seem the grudging testimony of simple honesty".