The surnames Giacalone, Giacardi, Giacaz, Giaccagli, Giaccaglia, Giaccaglini, Giaccardi, Giaccari, Giaccheri, Giaccherio, Giacchétti, Giacchi, Giacchin, Giacchini, Giacco, Giaccone, Giacconi, Giacheri, Giachero, Giachetti, Giachi, Giachin, Giachini, Giachino are all derived from the given name Giacomo. In some regions of Italy, contraction —that is, the loss of a syllable— gave rise to Giaco, and from there numerous suffixed variants emerged. The suffix lends the name different connotations.

The name Jacopo, derived from the Hebrew Giacobbe, together with the Greco-Byzantine variant Giacomo (very widespread during the Middle Ages), gave rise to a great variety of surnames of religious inspiration. Ya'āgob is the name of the patriarch Jacob in the Old Testament, and of the apostles James the Greater and James the Less in the New Testament. The Hebrew name, in turn, derives from Yah, an abbreviation of Yahweh = God, and probably gob = to protect, hence "God has protected".

Giacomo, Giacobo, Giacopo and Giacobbe are, in origin, the same name. It is a male given name, corresponding to the English James and Jacob.