The New York Times book of mathematics

Gina (occasional variants Geena, Gena, Jena, Jeana, Jeanna) is a feminine given name, in origin a hypocoristic form of names ending in -gina (by metanalysis of the latinate feminine suffix -ina), such as Luigina, Regina or Georgina, also of Virginia or Eugenia. The short form was popularized in the 1950s by the actress Gina Lollobrigida (1927−2023), whose birth name is Luigina. Lollobrigida became famous in 1953, from which year popularity of the given name Gina in the United States rose steeply, reaching a peak at rank 54 in 1967. Since the 1970s, it has declined steadily, falling below rank 1,000 in 2009.