This is considered by some scholars (such as P. Aubry) to be a result of Turkish influence, although others (such as R. P. Decevrens) consider it to be of great antiquity and use it as evidence in favor of a more rhythmic interpretation of Gregorian chant.
Some scholars, including P. Aubry, see this as the result of Turkish influence, while other scholars, such as R. P. Decevrens, regard it as very old and utilize it to bolster a more rhythmic understanding of Gregorian chant.