Properly, “Dog Latin” is just very bad Latin, a mongrel Latin, whence the name, composed of a mixture of Latin and English.
But in our own childhood, what we called dog Latin was a gibberish of decapitated English words, the initial letters transposed to the rear, plus “ay”; as, “Ohnny-jay ust-may o-gay ome-hay.”
In other areas this form of lopped English was called “hog Latin,” or “pig Latin,” possibly because the sound resembled the grunting of hogs.
