Just for the record:

The gzip format (defined in RFC 1952) allows storing the original filename (without the .gz suffix) in an additional field in the header (the FNAME field). Latin-1 (iso-8859-1) is required. It is ironic that this causes so much trouble, because it is never used. A gzip file without that field is prefectly valid. The gzip program for example stores the original filename by default but does not use it when decompressing unless it is explicitly told to do so with the -N/--name option. If no FNAME field is present in a gzipped file the gzip program just falls back on stripping the .gz suffix.