I saw an article recently where the author used the term "flogging a dead horse" where the term flogging was meant in the UK slang sense of "to sell".
It was accompanied by a drawing of a stuffed horse being sold at market with a sign along the lines of "fast, living horse for sale". (I can't find the article again).
Is this usage of the phrase valid? I always thought that the phrase was a slight rewording of "beating a dead horse" where "flog"/"beat" would mean to physically hit.