Douglas Harper's Etymology Dictionary
childish deformed language (there are many different versions), by 1889 (hog Latin in same sense by 1807).\n\nThe animals play quite an important part in the naming [of children's languages], as the hog, dog, fly, goose, pigeon, pig, all give names, with Mr. Hog leading. Among the names the Latins take the lead, and Hog Latin leads the list, being accredited as naming nearly as many languages as all the other names combined. Besides Hog Latin, there is Dog Latin, Pig Latin, Goose Latin, and Bum Latin. Then there is Greekish and Peddlers' French and Pigeon English. ... Very few can give any reason for the naming of the languages. In fact, no one can fully say where the great majority of names came from, for in most cases in the naming the following pretty well expresses the difficulty: "It was born before I was. I can't tell how young I was when I first heard of it."
["The Secret Language of Children," in "The North Western Monthly," October 1897]
Wiktionary
n. A type of wordplay in which (English) words are altered by moving the leading phonetic of a word to the end and appending ''-ay'' - however, if the word begins with a vowel then "-way" is suffixed with no leading phonetic change. (examples-right: examples="please be quiet or I'll cry" becomes "ease-play e-bay iet-quay or-way I'll-way y-cray")
Wikipedia
Pig Latin is a language game in which words in English are altered. The objective is to conceal the words from others not familiar with the rules. The reference to Latin is a deliberate misnomer, as it is simply a form of jargon, used only for its English connotations as a strange and foreign-sounding language.
Usage examples of "pig latin".
That he haunts the cathedral like a vile Protestant wraith, causing altar boys to spill the wine, dignified gentlemen to break wind during confession, bishops to lapse into pig Latin, and young mothers to agitate for birth control.
He wrote a draft, then painfully translated 'the letter into a mishmash of German, Russian, colloquial English, beatnik jive, literary allusions, pig Latin, and special idioms.