Giselly is of Germanic origin, derived from the name Gisela. It means 'pledge' or 'hostage', which were often given to ensure peace between tribes or nations in ancient times. The name gained popularity during the Middle Ages and was borne by several notable figures, including Saint Gisela of Hungary, who lived in the 10th century.
The number of girls named Giselly appears to be quite low and fluctuating over time, with peaks in 1997 and 2004, and a total of 18 births recorded between those years.