Analysis of information sources in references of the Wikipedia article "Girdle" in English language version.
Till, in the eighth or ninth century, the idea of an intended resemblance in detail between the Christian and Levitical vestments was first broached, the Girdle, naturally was either not worn at all (with the tunica talaris it was not necessary), or, when worn, was not visible, and was thought of only as a matter of convenience. In none of the early monuments of the West before A.D. 800, is any trace of it to be seen. But in the East we have mention of a Girdle as worn by deacons, early in the eighth century.
It has been said that it was not till the 8th century that we meet with the girdle as an ecclesiastical vestment in the strict sense of the word.