One of the many fanons in Pirates of the Caribbean is that Lieutenant Gillette's full name is Andrew Gillette, but that's not supported by any official source.
Fanon is a term used to refer to "fan canon" (of which the term is a portmanteau), or unoffical fiction.
It applies to certain "facts" that may have been accepted as a truth by a large number of fans, although not necessarily true, and thus either replaces an established canonical fact in the minds of those fans, or fills a plot-hole.
