How does "koe" mean "went over"?


> 山 を こえ、 たに を こえ、 うみ に でる と、 おに の ふね が ありました

It translates as

> They went over the mountains, and over the valleys  
>  And came out to the sea, and there was a devil boat

Why is it "koe" means "went over"?




こえ is a
[conjunctive](https://en.wiktionary.org/wiki/%E9%80%A3%E7%94%A8%E5%BD%A2) form
of the verb 越える{こえる} meaning roughly "to go past", "to go beyond", like
[山を越える](http://eow.alc.co.jp/search?q=%E5%B1%B1%E3%82%92%E8%B6%8A%E3%81%88%E3%82%8B).

