Barry, yes it should be "dog".
The new home computer keyboard is a laptop-like affair (ultra-short-key-travel), and I find myself tapping away merrily, and skipping letters as I go.
The saying is something I hear a lot, and appears to be a vernacular approximation of when educated people are tired of someone who has come to visit, and they say in an apparently polite way:
"please don't let me detain you any further"
...while hinting subtly that it is YOU who is detaining them...
Keith