The aim of the paper is to analyse the Italian medical terminology, in particular will be taken into consideration the link between names of different illnesses and rhetoric procedures that might have influenced their lexical form. The examples of medical nomenclature will enable to illustrate the attitude towards the concept of illness and to show the complexity of phenomena perception and the impossibility to understand them completely. For this reason literary tropes, especially metonymy, enable to create terminology, although it will be never enough sufficient to guarantee the highest precision of these concepts.