At the volumes I hear - introduction is a little understating the case.

But it does come from a long tradition of calling their wares. In the days of street cries ice cream sellers used to shout "Poco um Gecca" which morphed into Hokey Pokey. Well that was what I read but it may have been a fairly localised call & probably London.

round here "Greensleeves is my delight" (not).