You're learning 'Arrane Ben Drogh-hraghtalagh' or 'The Smuggler's Lullaby', by the looks of things, with the chorus:

Ogh hene, lhiannoo meein,
Caddil oo, my laala.

As you've not asked about the other words, you probably have just the 'Ogh hene'. The word, 'laala' is also rather doubtful, but is generally taken to mean 'hero'.

The 'gh' or 'ch' is as in Scottish 'loch', and hene is just 'heen'.

Really, 'Ogh hene' or 'Och hene' is just vocables, to rhyme with 'meein'. It's perhaps related to other Gaelic expressions such as 'Ochone', and could mean 'alas'. So the above chorus may be:

Alas, gentle child,
Sleep thou, my hero.

If it's another song, I'd be interested to know which one it is. As a matter of interest, it would be interesting to know where you found this song.

Hope this helps.

Shoh slaynt,

Bobby Bob