Ænon, more commonly written Aenon, is the site mentioned by the Gospel of John as the place where John was baptising after his encounter with Jesus.
"Ænon" is the Greek rendition of the Semitic term for "spring" or "natural fountain", like the Hebrew and Arabic 'ayn. In the water-poor Middle East, places owning a spring tend to be named after that water source, so that toponyms consisting of or containing the Construct state word "ein-" are common. The particular site mentioned in the Gospel of John is therefore closer identified as "Aenon near Salim". John 3:23 is the only place in the Bible where the name Aenon is found.
The name Aenon is commonly used amongst Baptist organizations and churches.
Both names, "Aenon" and "Salim", are not unique, and the Gospel text offers only two additional hints about where Aenon might be located: the most direct information is that "there was plenty of water there" (John 3:22), and the second is that it was west of the River Jordan because at Aenon John's disciples talk of the site where John first encountered Jesus as being "on the other side of the Jordan" (John 3:26), which is taken to mean east of the river. We also know from John 1:28 that that first encounter happened at "Bethany on the other side of the Jordan".
One possible location is near the upper source of the Wadi Fa'rah, an open valley extending from Mount Ebal to the Jordan River which is full of springs. There is a place called 'Ainun four miles north of the springs (see Easton's Bible Dictionary).