The authors differ as to the etymological origin of this surname. E. Rossoni proposes several hypotheses: it could derive from the Germanic name Gairovaldo, from the Languedoc name Guiraudos, or else from the Lombard name Warhard, compounded from the Germanic elements war(an) ("to protect") and hardhu ("strong, mighty"), with the sense "strong in protecting". F. De Laurentiis, by contrast, considers it derived from the given name Guarino.

According to Rossoni, the form Guaraldi would be characteristic of the Ferrara area —in particular of the localities of Cento and Ferrara—, in the region of Emilia-Romagna, with an additional presence in Tuscany, in the Arezzo area, and in Veneto. The variant Guaraldo, considerably rarer, records a small presence in the Rovigo area, in the localities of Lendinara, San Bellino and Lusia.