As many world languages, Turkic also has simple suffixes in terms of structure, as well as complex suffixes with controversial origins. Although some of these suffixes have been systematized and bound to certain rules, the emergence of some suffixes still remains a mystery. Old Uyghur, which is one of the historical periods of the Turkic language, has such an undeciphered suffix. The compound suffix of +DXrtI has been evaluated by some researchers to date; however, no definite conclusion has been reached regarding its origin and function. For this purpose, various structures in Altaic languages will be examined and a connection will be made between this suffix and the 'extraordinary' examples seen in Old Uyghur.