I'll go to the foot of our stairs
An exclamation of surprise.
This originated in the North of England. It did travel to others parts of the UK during the 20th century, notably the Birmingham area where it was commonplace, 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.
There are also less well-known alternatives with the same meaning - 'the back of our house' and 'the bottom of our garden'. All the variants were too low-status and colloquial to have been written down and I can find no printed examples of it until the late 20th century. The expression is certainly older than that and I have a clear recollection of my parents using it in the West Midlands in the 1950s and I would guess that it is older still.
Beyond that there's little more to tell. Exactly when the phrase was coined, by whom, and what it refers to, I don't know.