An incorrect variation on the exclaimation "D'oh."
As seen in the Simpsons episode "Burns' Heir," when Burns tried to convince Bart that his family doesn't miss him, and hires actors to portray them on a video feed. But, the Homer actor flubs his lines, saying "B'oh" instead of "D'oh."
Homer Actor: (odd voice) I do not miss Bart at all.
Marge Actor: (odd voice) I am glad he's gone.
Lisa Actor: (odd voice) As am I.
Homer Actor: (drops) sandwich B'oh!