THESAURUS
secret language
Aesopian language, Babel, Greek, argot, babble, cant, cipher, code, coded message, cryptoanalysis, cryptoanalytics, cryptogram, cryptograph, cryptographer, cryptography, double Dutch, garble, gibberish, gift of tongues, glossolalia, gobbledygook, invisible ink, jargon, jumble, noise, scramble, secret writing, slang, sympathetic ink