Gender: Feminine
Origin: Italian/Catalan
Meaning: “gem”
It (JEM-mah)
The name was originally used as a nickname in Medieval Italy, but gradually became an independent given name over the centuries.
Its earliest notable bearer was the wife of the 13th-century Italian poet, Dante Alighieri.
The name has been borne by at least four Catholic Saints, the most notable being St. Gemma Galgani, nee Maria Gemma Umberta Pia Galgani (1878-1903) . She was an Italian mystic who died in her 20s from Tuberculosis. Her cult became especially popular in Italy, Latin America and in Ireland after she had been canonized in 1940. In the 1950s, the name suddenly became mainstream in Ireland, no doubt due to the popularity of the recently canonized saint. Its usage in Ireland may have spread to the other British Isles. In the case of England, Scotland and Australia, the name probably became common due to its transparent meaning. The name was quite popular in Great Britain between the 70s, 80s and 90s, but has suddenly fallen out of favor.
Currently, Gemma is the 888th most popular female name in the United States, in fact, she just entered the top 1000 this past year (2008). She is the 75th most popular female name in Australia (2008).
The name has sometimes been anglicized to Jemma.
Other forms of the name include:
- Gemmina (Italian)
- Gema (Spanish: HEM-a; Portuguese ZHEM-a)
A few obscure masculine versions are Gemmino and Gemmo.
Gemma is also the name of a star.
Other notable bearers include: Gemma Atkinson, Gemma Craven, Gemma Hayes, Gemma Jones and Gemma Ward.
The designated name-day is April 11 (Italy).
Sources
Legitimate Baby Names 
Gema [ZHEM-a], albeit rare, is also used in Portugal.
Thanks