The question as I read it was when barrel aging of beer was first practiced. All beer stored in wood and for however long takes some flavor from the wood regardless of its prior use. Depending on the history and condition of the charred whisky cask acquired to house the beer first mentioned above, the whisky it used to hold may have a lot, some or no influence in the beer. An oak cask that never held anything before would however lend at least oak tannins to the brew, as e.g., the pin did that held Ron's IPA at Granite that used to be put on the counter there on some Friday nights in past years. So I read the question in the broader sense. If one takes it in the narrow sense of an ex-bourbon cask or Canadian rye cask or Scotch whisky cask that has residual flavours from the former contents, I agree that Upper Canada's pin of almost 20 years ago did not (as far as I know) have such a history.