In this short article we present the lexicological analysis of a sub-sample of male and female first names given to children in the “municipio” (municipality) of Tlalnepantla de Baz, Estado de Mexico, in the frame of a broader diachronic sociolinguistic study, that will coverall the xx century. This article only analyzes these years: 1935, 1940, 1945, 1950 and 1955. The corpus is based on the birth certificates of the civil registry office watched over by the “Oficialia” No. 1 (Registrar’s Office) of the before mentioned municipality. The whole study is registered in the Program of Support for Research and Technological Innovation Projects of the UNAM.The article will deal with the languages of the lexical units of the corpus, their morphological traits (derivation and composition phenomena observed) and the graphical form inwhich they were registered.We take as a starting point the general theory of the proper name in linguistics, as well as the studies that have dealt with that particular kind of name, the first name. The hypothesis we work with are a) the attribution of first names is not chaotic, but there is a norm linked to the moment and place in which the name is given; b) the canonical spelling form of names is generally observed; and finally c) the Hispanic names have not been displaced by the borrowings to other languages and it is the “intralinguistic” mechanisms of lexical creation what really allows the corpus to be renewed in its majority.