Glossolalia or speaking in tongues, according to linguists, is the fluid vocalizing of speech-like syllables that lack any readily comprehended meaning, in some cases as part of religious practice in which it is believed to be a divine language unknown to the speaker. Glossolalia is practiced in Pentecostal and Charismatic Christianity as well as in other religions. The term derives from glōssais lalō, a Greek phrase used in the New Testament meaning "speak in, with, or by tongues [i.e., other languages]" (Acts 2:4, 1 Corinthians 14:18).
The related phenomenon "xenolalia" or "xenoglossy" is when the language being spoken is a natural language previously unknown to the speaker.
"Glossolalia" is constructed from the Greek word γλωσσολαλία, itself a compound of the words γλῶσσα (glossa), meaning "tongue" or "language" and λαλέω (laleō), "to speak, talk, chat, prattle, or to make a sound". The Greek expression (in various forms) appears in the New Testament in the books of Acts and First Corinthians.
The exact phrase "speaking in tongues" has been used at least since the translation of the New Testament into Middle English in the Wycliffe Bible in the 14th century.Frederic Farrar first used the word "glossolalia" in 1879.
In 1972, William J. Samarin, a linguist from the University of Toronto, published a thorough assessment of Pentecostal glossolalia that became a classic work on its linguistic characteristics. His assessment was based on a large sample of glossolalia recorded in public and private Christian meetings in Italy, The Netherlands, Jamaica, Canada and the US over the course of five years; his wide range included the Puerto Ricans of the Bronx, the Snake Handlers of the Appalachians and the Spiritual Christians from Russia in Los Angeles (Pryguny, Dukhizhizniki).