The story
The word Latin derives from the language itself (though it is not linguistically related; that is an intentional misnomer), but the origin of pig is unknown.
Etymology from Wiktionary, CC BY-SA 4.0.
pig latin
Today it means: A type of wordplay in which (English) words are altered by moving the onset consonants of a word to the end and appending -ay [eɪ̯], except when the word begins with a vowel, in which case -way [weɪ̯] is suffixed with no leading phonetic change. Full definition →