tgz

from The Free On-line Dictionary of Computing (8 July 2008)

tgz
taz

   <filename extension, compression> (Or less often "taz", Tar
   GNU zip) A {filename extension} for a file or directory which
   has been archived with {tar} and then compressed with {gzip}.
   The full form ".tar.gz" is also common on proper {file
   systems} not limited to {8.3} file names.

   (1996-11-03)