The first known recorded mention of Eboracum by name is dated c. 95–104 AD and is an address containing the genitive form of the settlement's name, Eburaci, on a wooden stylus tablet from the Roman fortress of Vindolanda in what is now the modern Northumberland. During the Roman period, the name was written both Eboracum and Eburacum (in nominative form) .
The name Eboracum comes from the Common Brittonic Eburākon, which means "yew tree place". The word for "yew" was *ebura in Proto-Celtic (cf. Old Irish ibar "yew-tree", Irish: iúr (older iobhar), Scottish Gaelic: iubhar, Welsh: efwr "alder buckthorn", Breton: evor "alder buckthorn"), combined with the proprietive suffix *-āko(n) "having" (cf. Welsh -og, Gaelic -ach) meaning "yew tree place" (cf. efrog in Welsh, eabhrach/iubhrach in Irish Gaelic and eabhrach/iobhrach in Scottish Gaelic, by which names the city is known in those languages). The name was then Latinized by replacing the Celtic neuter nominative ending -on by its Latin equivalent -um,a common use noted also in Gaul and Lusitania. Various place names, such as Évry, Ivry, Ivrey, Ivory and Ivrac in France would all come from *eburacon / *eburiacon; for example: Ivry-la-Bataille (Eure, Ebriaco in 1023–1033), Ivry-le-Temple (Evriacum in 1199) Évry (Essonne, Everiaco in 1158), etc.
The Roman conquest of Britain began in 43 AD but advance beyond the Humber did not take place until the early 70s AD. This was because the people in the area known as the Brigantes by the Romans became a Roman client state. When their leadership changed becoming more hostile to Rome, Roman General Quintus Petillius Cerialis led the Ninth Legion north from Lincoln across the Humber. Eboracum was founded in 71 AD when Cerialis and the Ninth Legion constructed a military fortress (castra) on flat ground above the River Ouse near its junction with the River Foss. In the same year Cerialis was appointed Governor of Britain.
A legion at full strength at that time numbered some 5,500 men, and provided new trading opportunities for enterprising local people, who doubtless flocked to Eboracum to take advantage of them. As a result, permanent civilian settlement grew up around the fortress especially on its south-east side. Civilians also settled on the opposite side of the Ouse, initially along the main road from Eboracum to the south-west. By the later 2nd century, growth was rapid; streets were laid out, public buildings were erected and private houses spread out over terraces on the steep slopes above the river.