From The Fabulous Fibonacci Numbers by A.S. Posamentier and I. Lehmann (Prometheus Books, New York (2007), pp. 17-18):
Leonardo Pisano - or Leonardo of Pisa, Fibonacci - his name as recorded in history, is derived from the Latin "filius Bonacci," or a sunson of Bonacci, but it may behave been more likely derivederived from "de filius Bonacci," or family of Bonacci. He was born to GuilielmoGuglielmo (William) Bonacci and his wife in the port city of Pisa, Italy, around 1175, shortly after the start of construction of thea famous bell tower, the Leaning Tower of Pisa.
The authors also indicate in a footnote that
it is unclear who first used the name Fibonacci; however, it seems to be attributed to Giovanni Gabriello Grimaldi (1757-1837) at around 1790, or to Pietro Cossali (1748-1815).