The name hedgehog came into use during the fifteenth century.
The hedge part of their name comes from where they build their nests: hedges, bushes and shrubs. The hog part comes from its pig-like snout and the snorting and grunting sound they make.
The hedgehog was not always called a hedgehog, though. In mediaeval times they were called urchins, and in some British dialects they still are. We are left with the remnants of this in the name of sea urchins.
And finally, it is rare to see a number of hedgehogs together but if you do it is called an array.