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 sun of Bonacci, but it may be more likely derive from "de filius Bonacci," or family of Bonacci. He was born to Guilielmo (William) Bonacci and his wife in the port city of Pisa, Italy, around 1175, shortly after the start of construction of the 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).