It will be some pro IRA, sectarian chant. Maybe some rebel victory song celebrating the death of a British soldier or something like that. Lovely.
I'm afraid you misheard it, mate! They don't sing "Paddy McCourt's barmy army" they sing "Paddy McCourt's Fenian army" I'd hate our club ever to be associated with either of the ugly sisters(Celtic and Rangers), some of the songs their "fans" sing are sickening.
Barnsley and Rangers have ties, some of the Barnsley lads were at the Rangers game the other week. Quite a few follow them in Europe, a few years ago it was a loophole for getting round the banning orders.