Greetings!  My “bookstumper” originates from a story my grandmother read to my brother and me in the 60s.  I don’t know how old the story is; I think the story might have been in an anthology of short stories.  The operative phrase is “I fell down in the mud.”  It could even be a bit of a poem, as I remember a dialogue between seemingly mother and son, as the mother rages on how could the boy have done this, how could he have gotten his clothes so dirty, etc.  After each of these Mom rages, the boy simply says, “I fell down in the mud.”  My brother and I have not been able to find hide nor hair of this on Google and other search engines.