Boyd’s Bible Dictionary:

(eye). (1) A landmark on eastern boundary of Canaan (Num. 34:11). (2) A Levitical city in south Judah and then in Simeon (Josh. 15:32; 19:7; 21:16). Ashen (1 Chron. 6:59).

Concise Bible Dictionary:

The word ain signifies an “eye,” or a “fountain”; it is often used as a prefix, and signifies a fountain of living water in distinction from a well, cistern or tank. It is mostly represented by the prefix EN.
1. Ain, a fountain in the extreme north. There is a fountain still called Ain el-Asy, ten miles S.W. of the ancient Riblah (Num. 34:11).
2. One of the Levitical cities in the south. It was originally given to Judah but afterward allotted to Simeon (Josh. 15:32; Josh. 19:7; Josh. 21:16; 1 Chron. 4:32). In 1 Chronicles 6:59 the margin intimates that ASHAN is the same as AM as a Levitical city, although in 1 Chronicles 4:32 AM and Ashan are both mentioned.

Jackson’s Dictionary of Scripture Proper Names:

an eye: fountain