🔼The name Decapolis in the Bible
The name Decapolis belonged to a region almost exclusively east of the Jordan, so technically not part of the Roman province of Judea or even of Israel. It consisted of a, what seems, arbitrary cluster of cities, which included Gerasa (possibly connected to the land of the Gerasenes, mentioned in Mark 5:1 and Luke 8:26), Gadara (possibly connected to the land of the Gadarenes, mentioned in Matthew 8:28), Scythopolis (probably the same as the Biblical Beth-shean, which was the only city of the west side of the Jordan), Philadelphia and possibly Damascus, the capital of Syria.
How many proper urban centers there actually were in Decapolis isn't clear. Several contemporary ancient historians such as Pliny the Elder, Josephus and some others list up to nineteen different names, but, for instance, Pliny lists Damascus while Josephus doesn't.
What is clear, however, is that Decapolis was notorious for its blending of Semitic and Greco-Roman cultures, even to the extent that diffusion and assimilation on both sides formed a recognizable Decapolitan sub-culture. The cities were autonomous, insofar that word applied to a Rome-ruled existence, but enjoyed a blooming trade among each other and neighboring societies.
The name Decapolis occurs three times in the Bible. The gospel of Matthew mentions that in His early ministry, Jesus attracted people from Galilee, Decapolis, Jerusalem and Judea (Matthew 4:25). These four names provide quite some geographical overlap, and it seems plausible that Matthew meant to say that people from four major and differing schools of thought found themselves interested in Jesus.
All three synoptic gospels mention the story of the man named Legion (by Matthew portrayed as two unnamed men), whose exorcism is also a cunning commentary on the goings on of the times (Matthew 8:28-34, Mark 5:1-20, Luke 8:26-40; see our article on the name Legion for more details). Only Mark adds that the man formerly known as Legion began to proclaim in Decapolis what great things Jesus had done for him (Mark 5:20). Mark is also the only one who reports that Jesus went from Tyre to Sidon to the Sea of Galilee and into Decapolis, where He healed a deaf-mute man (Mark 7:31).
🔼Etymology of the name Decapolis
The name Decapolis consists of two elements. The first part is the common cardinal number δεκα (deka), meaning ten:
The second part of our name is the word πολις (polis), meaning city:
The name Decapolis does not mean Ten Cities, because (a) there were more than ten, and (b) the word for city is singular. The name Decapolis appears to reflect the idea that its cluster of cities together formed a closed unit, which might as well have existed as if behind its collective wall. The word δεκα (deka), in this case, also doesn't denote a quantity between nine and eleven, but rather the whole of one, arbitrarily large collection.
All this considered it's difficult to come up with a equivalent translation; the English language simply doesn't feature the mechanisms used to form this name. But to the locals back then, the name Decapolis probably sounded like the name The United States does to us.