The name Giselly is a feminine given name derived from the Germanic name Gisela, which is a compound of the elements "gis" meaning "pledge" or "hostage" and "hild" meaning "battle". It is believed to have originated during the Middle Ages, around the 6th to 8th centuries AD, among the Frankish and Germanic tribes of central and western Europe.

Gisela was a popular name among the Frankish nobility and royalty, and it is recorded in various historical documents from that era. One of the earliest known bearers of the name was Gisela, the daughter of King Lothar II of Lotharingia, who lived in the 9th century AD.

The name Giselly is a variant spelling that emerged later, likely as a result of linguistic and cultural influences as the name spread across different regions and languages. It is possible that the name was introduced to other parts of Europe during the Middle Ages through trade, migration, or political alliances.

Notable historical figures named Giselly or a similar variant include Gisela of Burgundy, a queen consort of Hungary in the 11th century, and Gisela of Merania, a German princess and duchess of Bavaria in the 12th century. In the 16th century, there was a Spanish noblewoman named Gisela de Alencastre, and in the 17th century, a German nun named Gisela von Kerssenbroch wrote a chronicle of her convent's history.

One of the earliest recorded instances of the spelling "Giselly" can be found in the records of a Flemish family from the 16th century, where a daughter was named Giselly. Another notable bearer of the name was Giselly de Villiers, a French writer and translator who lived in the late 18th century.

Over the centuries, the name Giselly has been used across various cultures and regions, including France, Germany, Spain, and other parts of Europe, as well as in Latin American countries influenced by Spanish and Portuguese naming traditions. While its popularity has fluctuated, the name has maintained a presence throughout history, reflecting its Germanic roots and the cultural exchanges that shaped its evolution.