The authors agree that the surname derives from the medieval feminine name Gemma, from late Latin, meaning "gem" or "precious stone". It is an auspicious and affectionate name, used for a daughter in a way similar to other names linked to objects of value, such as Margherita, Perla or Diamante. The name already appears documented in epigraphic inscriptions under the forms Gemma and Gemmula.

E. Rossoni provides a concrete documentary example: a deed of the year 955 written in Cava dei Tirreni mentions a certain Gemma uxor mea, which attests to the use of the name in the early Middle Ages. Rossoni also notes that the surname presents independent stems of origin in the Mantua area, the La Spezia area, the Naples area, the Catania area, Lazio and Apulia, especially in the Salento area —the southernmost zone of that region, in southern Italy—.

A. Bongioanni and E. De Felice agree in noting the southern variant Ièmma and in highlighting that the surname spread mainly in southern Italy and in Tuscany. Both mention a saint of this name, who died in 1429 and is venerated in Abruzzo, whose feast is celebrated on 12 May.

F. Miranda broadens the meaning of the Latin etymon and indicates that Gemma could also refer to "bud", "shoot" or "source of life", and suggests that the surname probably arose as a byname applied to a person of great worth or social importance.