It is a term relating to the direct style favoured by Warren Gatland, the Wales head coach, during the last British and Irish Lions tour.
It has since been used to describe the tactics of his Wales team, but O'Connell is adamant that there is much more to today's RBS 6 Nations opponents than brute force. He has warned his team not to risk becoming complacent when the Welsh arrive in Dublin.
"I think [Warrenball] is a bit of an unfair tag," said the Ireland lock. "Because they're big men you just think their game's all about physicality. But there's an incredible amount of subtlety to what they do.
"I remember seeing that in the last two tours. Everyone just thinks they launch big men into midfield as the first phase for every play. It is something they do, but they do it with a lot of subtlety, they have a lot of animation out the back, pulling defenders away.
"I think they have incredibly skilful players, incredibly talented players all across the pitch, and I suppose the fact they're all big men just adds to that. Warrenball made an interesting headline during the summer, but there's a lot more to their game than that."
It is something which the Welsh wish to prove themselves when they take on the Irish in the second round of Six Nations matches. "There is pressure on us," said Gethin Jenkins, the Wales prop, who has recovered from a knee injury and returns to win his 102nd cap.
"That is the pressure we put on ourselves to win the title, so I suppose the same is the case this year. We have put the pressure on ourselves. You've got belief. It's a big change in mentality from when I first started."
TEAM. Ireland v Wales (Aviva Stadium, Dublin, today, 2.30)
IRELAND R Kearney (Leinster), A Trimble (Ulster), B O'Driscoll, G D'Arcy, D Kearney (all Leinster), J Sexton (Racing Metro), C Murray (Munster), C Healy (Leinster), R Best (Ulster), M Ross, D Toner (both Leinster), P O'Connell (capt), P O'Mahony (both Munster), C Henry (Ulster), J Heaslip (Leinster)
Substitutes S Cronin, J McGrath, M Moore (all Leinster), D Tuohy (Ulster), T O'Donnell (Munster), I Boss (Leinster), P Jackson (Ulster), F McFadden (Leinster)
WALES L Halfpenny (Cardiff Blues); A Cuthbert (Cardiff Blues), S Williams (Scarlets), J Roberts (Racing Metro), G North (Northampton Saints); R Priestland (Scarlets), M Phillips (Racing Metro); G Jenkins (Cardiff Blues), R Hibbard (Ospreys), A Jones (Ospreys), A Coombs (Newport Gwent Dragons), A-W Jones (Ospreys), D Lydiate (Racing Metro), S Warburton (Cardiff Blues, capt), T Faletau (Newport Gwent Dragons).
Substitutes K Owens (Scarlets), P James (Bath), R Jones (Scarlets), J Ball (Scarlets), J Tipuric (Ospreys), R Webb (Ospreys), J Hook (Perpignan), L Williams (Scarlets)