two different songs, different lyrics and tunes
same mountain
Kickham's song is usually spelled "Slievenamon"
Dominic Behan's verses are translation of an Irish Gaelic song, also sometimes known as "Is oth liom féinig". Look up Slievenamon" on Mudcat for more discussion and for the Irish language lyrics as well; there's a clickable link near the top of this page (Lyr req: Slievenamon)