The progymnasmata were preliminary exercises of writing used by students at the beginnings of rhetorical training in order to learn the proceedings of textual composition. They constituted the practice of teaching writing in Greek and Latin schools. However, in the face of four manuals and numerous Greek papyri containing exercises done, we have little information about the Latin exercises. This information is related to the sources of Quintilian (Inst. I, 9; II, 4) and Suetonius (Gramm. 4, 6-8; 25, 8). Here we find the definition of some simple exercises preparatory destined by Quintilian to the care of the grammarian. In addition to anecdote (chria) and statement (sententia) Quintilian refers to a similar exercise that begins by paraphrasing and elaborating texts read in class. For this exercise the manuscripts provide two variants, ethologia or aetiologia, both plausible. Through philological analysis of the text, but also through a historical and critical examination of the rhetorical tradition, the paper is intended to highlight the potential of the solution aetiologia. The survey consists of two parts: in the first is discussed and excluded the proposal ethologia, which is unsuitable because it outlines an exercise, the "description of the character", too complex for a start-up phase to writing. In the second part, it is argued in favor of reading aetiologia proposing the identification of the exercise with the expansion work of an anecdote (chria) or motto (sententia) by indicating the reasons given in his favor. For this type of exercise on chria and sententia it may indicate relations with the Progymnasmata of Theon, while the technical term aetiologia is taken from the manual of rhetorical art where it indicates a figure of thought. It so happens that a particular type of exercise is identified by a figure of speech. [ABSTRACT FROM AUTHOR]