X+子 may be a phrase, compound or root+suffix, which reflects the results of lexicalization or even grammaticalization during the process of disyllabification. The compounding process of X+子 is called lexicalization, while 子 further developed into a suffix is grammaticalization. From diachronic perspective, there are two findings in this paper: (1) the variety of X+子shows different degrees of lexicalization, and their characteristics are: a) the idiomatization, b) the fusion of lexical meanings, and c) semantic change caused by metaphor or metonymy; (2) the concept of semi-affix shows a continuous and gradual change of X+子 from a root of a compound into a suffix during the six dynasties. One of the functions of suffix 子 is a nominalizer; however, after checking the twenty five examples in the historical documents, only six of them are nominalized by 子, while the others are resulted from disyllabification.