The authors agree that the surname derives from a personal name of Germanic origin, whose base is formed by the elements gaira- ("spear") and hardhu- ("strong, valiant"), with the original meaning "strong or valiant with the spear". E. De Felice specifies that the forms in -aldo and -oldo also incorporate the element walda- ("mighty, prince, chief"), and distinguishes traditions according to origin: Garardo and Galardo answer to the Lombard tradition; Gherardo and Ghelardo, to the Frankish or Old Germanic one, probably Alemannic; Gerardo and Girardo, to the more recent French tradition. The form Ghelardo arises from Gherardo through dissimilation of r-r into l-r.

E. Rossoni notes that all these forms would derive from the medieval name Gerhard, Latinized as Garardus or Ghirardus, documented in 1174 in Brescia, in 1100 in the Catalogus Baronum of Caserta and around 1300 in the Historia Langobardorum Beneventanorum. As for distribution, Rossoni indicates that Gherardi is typical of the strip between Emilia-Romagna and Tuscany, with an isolated pocket in the Bergamo area; Ghirardi is very widespread in northern Italy, especially in Lombardy, the Turin area and the Parma area.

The surname is held to have a related antecedent in Ghirardelli, and to display diverse regional forms: Girod in the Aosta Valley, Giraudo in Piedmont, Ghiroldi and Geroldi in Lombardy, and Ierardi and Ciraldo in southern Italy.