E. De Felice and the Web Cultura Barocca source —the latter explicitly citing De Felice— agree that this is a surname derived from the old personal name of Germanic origin Aicardo, documented in northern Italy in the year 880 and later in Genoa, where it frequently appears in medieval Latin deeds of the 11th and 12th centuries, in the forms Agicardus and Aicardus. Both note that in the original Germanic name —already Gothic (a Gothic name Aichar(d) or Aicard is attested) and Lombard, but re-spread by the Franks— the first element is the adjective *aig- ("own, characteristic; personal, original"; German eigen). E. De Felice adds that, less probably, the first element could be the noun *agi- ("terror"), and that the second element is *hardhu- ("strong, brave, bold"), so the original meaning would be "endowed with personality and valour" or "who stands out for his own valour". He adds that Icardi may not be a variant of Aicardi, but rather have as its first element the Germanic hypocoristic Ico or Icho, and that this surname type is very common in France in the forms Achard and Ichard, and, in the South, Aicard and Icard. He characterises the surname as Ligurian and Piedmontese.

E. Rossoni agrees on the medieval Germanic origin and notes that it derives from the name Aicardus, documented in a deed of sale of September 1045 in the Brescian Diplomatic Code, where a notary signs with that name. He adds that at the beginning of the 15th century the bishop of Novara Bartolomeo Aicardi Visconti is documented.

P. Regati provides a geographical perspective by noting that it is a surname typical of Oneglia.