A broad group of Italian surnames has its origin in the ancient Germanic personal name Gerhard, documented in Italy from the early Middle Ages through various Latinized and Italianized forms (Gerardus, Gherardus, Girardus, Gilardus).

The name Gerhard is compounded from two Germanic elements:

• *gaiza / gaira = "spear"
• *hardhu = "strong, brave, bold"

Its original meaning can be interpreted as "strong with the spear", "valiant warrior" or "powerful fighter", and it belongs to a broad repertoire of names of clearly military and heroic stamp, widespread among the Germanic peoples and later adopted in the Italian territories during Lombard, Frankish and Alemannic rule.

When a surname is said to derive from a Lombard, Frankish or Alemannic tradition, the reference is to different historical and linguistic stages in the adaptation of one and the same Germanic name in Italy.

• The original name, of Germanic root, sounded approximately like Gerhard or Gairhard, with a hard initial g and a well-marked r, and meant "strong with the spear".
• In the Lombard period (6th–8th centuries), these names were Latinized in a fairly direct and conservative way, giving forms such as Garardo or Gherardo, harder in sound and closer to the Germanic original.
• With the arrival of Frankish influence (8th–10th centuries), tied to the Carolingian world and to Old French, the name begins to soften: the initial g is palatalized and forms such as Gerardo or Girardo emerge, more in keeping with the Romance ear. To palatalize is for a "hard" sound to become softer, because the tongue moves closer to the palate in pronouncing it (hence the term).
• Later, in areas of northern Italy with Alemannic and Alpine influence, and in contact with medieval French, that palatalization is consolidated still further, giving rise to forms such as Gilardo and finally Gilardi, by then fully Italianized.

Thus, surnames such as Gherardi, Girardi and Gilardi do not represent different families, but different historical ways of pronouncing and writing the same ancient name, fixed as surnames at different times and in different regions.

According to E. De Felice, the variants with Ger- / Gher- / Ghir- represent the oldest forms, while those beginning with Gi- reveal a palatalization of French influence, later in date, which spread especially in northern and central Italy.

In northern Italy, especially in Piedmont and in the Alpine areas in contact with the Franco-Provençal sphere, a phonetic phenomenon is recorded whereby the group -ardo evolves towards -audo. This change answers to a dialect adaptation of the sound, in which the vowel a becomes a diphthong and the r loses force, giving rise to more open forms such as -audo. For this reason, surnames such as Girardo / Gilardo generated variants such as Giraudo and Giraudi, which do not indicate a different origin, but a regional evolution of the same Germanic name (Gerhard). This process is common in Piedmontese surnames and explains the historical coexistence of both endings within a single family group.

For his part, E. Rossoni stresses that this Germanic name gave rise to one of the largest groups of surnames in the Italian panorama, with a very broad distribution but with strong regional concentrations according to the variant adopted.

Surnames derived from the Germanic name Gerhard

From this same personal name derive, among others, the following surnames:

• Gerardi: central and northern Italy
• Gherardi: Tuscany, Emilia-Romagna
• Ghirardi: Lombardy, Veneto
• Girardi: Trentino-Alto Adige, Veneto
• Gilardi: Lombardy, Piedmont
• Giraldi: Veneto
• Gherardini: Tuscany
• Ghirardini: Emilia-Romagna
• Gilardini: Lombardy
• Gilardoni: Lombardy
• Gilardino: Piedmont
• Gilardone: Piedmont (the Alessandria area)
• Girardelli: Trentino-Alto Adige, Veneto
• Ghirardelli: Emilia-Romagna
• Giraudo: Piedmont (Cuneo)
• Giraudi: Piedmont
• Giraud: the Aosta Valley

In general terms:

• The Gher- / Ghir- forms predominate in northern and central Italy.
• The Ger- / Gir- forms show a broader distribution, including the centre-south.
• The Gil- forms (such as Gilardi) are characteristic of northern Italy, especially Lombardy and Piedmont, and reflect a more recent phonetic evolution.

The differences between Gerardi, Gherardi, Girardi, Gilardi and their derivatives do not answer to different origins, but to regional linguistic adaptations of the name Gerhard.