Abstract: The corpus of documents from Catalonia from the 9th–12th centuries is outstanding from the linguistic point of view. The language of these sources combines Latin words from the Roman period with innovations from the Middle Ages, a phenomenon that we will illustrate through the nouns that designate merchants. This study will help to understand the Latin of medieval Catalonia, reveal aspects of the life of merchants and offer relevant testimonies for the study of preliterary Catalan.