Adopted by Liverpool in early sixties after Gerry & the Pacemakers (from Liverpool) released it as a single.
Stolen and sung by nearly every club at some point thereafter (I'm almost certain even Rangers sung it). Definitely NOT a Celtic song originally - eventually most clubs moved on to other songs/chants, Celtic continued to sing it and 'adopted' it as their own.
Another copycat - 'the Poznan' (though that might be the Huddle "something else" refers to).