Cross-reference information (for FWEAVE) includes the Table of Contents (’c’), the Index (’i’), and the Module List (’m’). The option ‘-x’ eliminates all of that information. The option ‘-xletters’ eliminates the piece of information corresponding to each letter in the list. For example, ‘-xim’ eliminates the Index and the Module List.
Another possibility is to say ‘-xu’, which prevents cross-references from unnamed sections (begun with ‘@a’ or ‘@A’) from appearing in the Index.