The meaning of 아리랑 is not known. And, some historians are studying it, but still controversial. One of the probably theories is that it is a name of a mountain pass. The lyrics of the song 아리랑 says
아리랑 고개를 넘어간다.
고개 means a mountain pass.
But there are many different version of songs 아리랑 in variou areas. In lyric of some song says:
아리 아리랑 쓰리 쓰리랑 아라리가 났네...
아리랑 doesn't sound like a name of mountain pass here. Some historian says that 아리 is a noun and 랑 is suffix to represent 'together'.