According to the 2004 screenplay (revised by James Schamus), Lureen misunderstands Jack when he xecrates:
Jack breathlessly enters the room.
On seeing Lureen and the baby, he stops short.
Jack: "Lureen. Well, well, Jesus Christ almighty (sic)."
Lureen: "I thought we agreed to call him Bobby. But if you want to call him Jesus Christ almighty (sic), I suppose I'd consider it."