The word cynocephaly is taken (through Latin) from the Greek word κῠνοκέφᾰλοι kynokephaloi, from kyno– (combining form of κύων kyōn) meaning "dog" and κεφαλή kephalē meaning "head".
The same "dog" root is found in the name Cynomorpha ("dog-shaped") for a sub-group of the family Cercopithecidae, which contains many species of macaques and baboons.
Ancient Greece and Egypt
Cynocephaly was familiar to the Ancient Greeks from representations of the Egyptian gods, Duamutef (Son of Horus), Wepwawet (The opener of the ways), and Anubis (the Egyptian god of the dead). The Greek word (Greek: κῠνοκέφᾰλοι) "dog-head" also identified a sacred Egyptian baboon with the face of a dog.
Reports of dog-headed races can also be traced back to Greek antiquity. In the fifth century BC, the Greek physician Ctesias wrote a detailed report on the existence of cynocephali in India, known as Indica. Similarly, the Greek traveller Megasthenes claimed to know about dog-headed people in India who lived in the mountains, communicated through barking, wore the skins of wild animals and lived by hunting. Herodotus reports claims by ancient Libyans that such creatures inhabit the east of their lands, as well as headless men and various other anomalies.
The best estimate for the place where the battle between the Argonauts and the Cynocephali took place is modern day North Serbia, or South Hungary.
The cynocephali offered such an evocative image of the magic and brutality deemed characteristic of bizarre people of distant places that they kept returning in medieval literature. Augustine of Hippo mentioned the cynocephali in City of God, Book XVI, Chapter 8, in the context of discussing whether such beings were descendants of Adam; he considered the possibility that they might not exist at all, or might not be human (which Augustine defines as being a mortal and rational animal: homo, id est animal rationale mortale), but insisted that if they were human they were indeed descendants of Adam.
Augustine City Of God https://en.wikipedia.org/wiki/The_City_of_God_(book)
The City of God Against the Pagans (Latin: De ciuitate Dei contra paganos), often called The City of God, is a book of Christian philosophy written in Latin by Augustine of Hippo in the early 5th century AD.
**Hippo is Greek for Horse
Cynocephali also figure in medieval Christian world-views. A legend that placed St. Andrew and St. Bartholomew among the Parthians presented the case of "Abominable", the citizen of the "city of cannibals... whose face was like unto that of a dog." After receiving baptism, however, he was released from his doggish aspect.
Cynocephalus St. Christopher
In the Eastern Orthodox Church, certain icons covertly identify Saint Christopher with the head of a dog. The background to the dog-headed Christopher is laid in the reign of the Emperor Diocletian, when a man named Reprebus, Rebrebus or Reprobus (the "reprobate" or "scoundrel") was captured in combat against tribes dwelling to the west of Egypt in Cyrenaica. To the unit of soldiers, according to the hagiographic narrative, was assigned the name numerus Marmaritarum or "Unit of the Marmaritae", which suggests an otherwise-unidentified "Marmaritae" (perhaps the same as the Marmaricae Berber tribe of Cyrenaica). He was reported to be of enormous size, with the head of a dog instead of a man, apparently a characteristic of the Marmaritae. This Byzantine depiction of St. Christopher as dog-headed resulted from their misinterpretation of the Latin term Cananeus (Canaanite) to read canineus, that is, "canine". The German bishop and poet Walter of Speyer portrayed St. Christopher as a giant of a cynocephalic species in the land of the Chananeans (Canaan in the New Testament) who ate human flesh and barked. Eventually, Christopher met the Christ child, regretted his former behavior, and received baptism. He, too, was rewarded with a human appearance, whereupon he devoted his life to Christian service and became an athlete of God, one of the soldier-saints. There are some rare icons that depict this martyr with the head of a dog. Such images may carry echoes of the Egyptian dog-headed god, Anubis; and Christopher pictured with a dog's head is not generally supported by the Orthodox Church.