Where does the phrase well I'll go to the foot of my stairs come from?

"This originated in the North of England. It did travel to others parts of the UK during the 20th century, but not much further, and is little known in other parts of the English-speaking world. It is now less used than previously, although it is still staple fare for any writer wishing to write a part for a stage northerner.

The foot of the stairs was en route to the lavatory, as was, in the days of the outside privy, the less well-known alternatives, 'the back of our house' and 'the bottom of our garden'. The implication of the speaker's destination suggests that the real meaning was 'I was so surprised that I soiled myself and need to visit the lavatory to clean up'."