Eiruv

Rabbi, where does the term "Eiruv" come from? Is it just a "loophole" to do something which isn't written anywhere to get by some of the basic Shabbos/Yom Tov rules, or is it actually written somewhere? If it is written, is it explained specifically? Thank you.

Even though the idea of an Eiruv sounds like a loophole that is used to allow people to carry in a place that they are not allowed to, that is not a strictly accurate description. A loophole implies that there is something not quite right about what is being done but that it cannot be defined as being illegal. An Eiruv is not like that at all. In Jewish Law an Eiruv is a completely legal method of surrounding an area and turning it into what is known as a private domain as opposed to a public domain. It is a concept that is discussed in the Mishna and Talmud and there is even an entire tractate  - called Eiruvin (the plural of Eiruv) named after the concept that deals with the many laws and methods of making an Eiruv that follows the Halacha.