Heinz 57 is a playful term kept to refer to mixed breed dogs. So basically Heinz 57 dogs are dogs from multiple ancestries. The naming secret as Heinz 57 lies in the slogan of the company HJ. Heinz “57 varieties”.
Back in the 1950s Heinz the popular ketchup manufacturing company advertised their 57 varieties of pickles available with them with the slogan ‘Heinz 57’ and then some quick-witted people started to nickname the Mongrel dog breeds with Heinz 57 due to its 57 varieties and mixed lineage.