The name Gennaro originates from the Italian language and has its roots in the Late Latin name Ianuarius. This name is derived from the Latin word "ianua," meaning "door" or "gate." The name likely has a connection to the Roman god Janus, the god of beginnings, transitions, and entrances.

In ancient Roman culture, the month of January was named after Janus and was considered the first month of the year, serving as a symbolic entrance or gateway to the new year. This association with beginnings and transitions may have influenced the development of the name Gennaro.

The earliest recorded use of the name Gennaro can be traced back to the early medieval period in Italy. One of the earliest notable figures with this name was Gennaro Maria Sarnelli (1598-1618), an Italian Catholic prelate who was canonized as a saint by Pope Pius IX in 1861.

Another prominent historical figure named Gennaro was Gennaro Annese (1604-1678), an Italian anatomist and physician who made significant contributions to the study of the human brain. He is known for his detailed descriptions and illustrations of the brain's ventricles and other structures.

During the Renaissance period, the name Gennaro gained popularity among Italian artists and intellectuals. One notable bearer of this name was Gennaro Greco (1663-1714), an Italian painter and architect who worked in Naples and contributed to the development of the Baroque style in southern Italy.

In the realm of opera, Gennaro is the name of a character in Giuseppe Verdi's opera "Luisa Miller." The opera, based on a play by Friedrich Schiller, premiered in 1849 and features Gennaro as a young lover caught in a tragic love story.

Another historical figure named Gennaro was Gennaro Contaldo (1854-1909), an Italian chef and restaurateur who played a significant role in introducing authentic Neapolitan cuisine to London in the late 19th century. His restaurant, Cafe Napolitana, became a popular destination for Italian cuisine in the city.