It is sometimes called Southrn Ireland, though is more commonly reffered to as 'down south', 'the south', sometimes even 'the free state' (from people in Northern ireland). Likewise people from the republic often call Northern Ireland 'up north', 'the north' etc. I have heard English people call the South 'Eire'.
You can't say that it's never called Southern Ireland. You're friend is being pedantic, most of his compatriots wouldnt care at all.
You can't say that it's never called Southern Ireland. You're friend is being pedantic, most of his compatriots wouldnt care at all.