Set the title for GNOME terminal emulator.

Define the title for the current terminal tab

Inspect GNOME terminal source code to identify the escape characters.

TerminalScreen *
terminal_screen_new (GSettings       *profile,
                     const char      *title,
                     double           zoom)
  g_return_val_if_fail (G_IS_SETTINGS (profile), nullptr);

  TerminalScreen *screen = (TerminalScreen*)g_object_new (TERMINAL_TYPE_SCREEN, nullptr);

  terminal_screen_set_profile (screen, profile);

  vte_terminal_set_size (VTE_TERMINAL (screen),
                         g_settings_get_int (profile, TERMINAL_PROFILE_DEFAULT_SIZE_COLUMNS_KEY),
                         g_settings_get_int (profile, TERMINAL_PROFILE_DEFAULT_SIZE_ROWS_KEY));

  /* If given an initial title, strip it of control characters and
   * feed it to the terminal.
  if (title != nullptr) {
    GString *seq;
    const char *p;

    seq = g_string_new ("\033]0;");
    for (p = title; *p; p = g_utf8_next_char (p)) {
      gunichar c = g_utf8_get_char (p);
      if (c < 0x20 || (c >= 0x7f && c <= 0x9f))
      else if (c == ';')

      g_string_append_unichar (seq, c);
    g_string_append (seq, "\033\\");

    vte_terminal_feed (VTE_TERMINAL (screen), seq->str, seq->len);
    g_string_free (seq, TRUE);

  vte_terminal_set_font_scale (VTE_TERMINAL (screen), zoom);
  terminal_screen_set_font (screen);

  return screen;

For more details inspect Operating System Commands

Use echo to interpret these escape characters and set title for current tab.

$ echo -ne "\033]2;GNOME terminal - tab 3\007"

Define the title for new terminal window

Display help information for gnome-terminal.

$ gnome-terminal --help-all
  gnome-terminal [OPTION?] [-- COMMAND ?]

Help Options:
  -h, --help                      Show help options
  --help-all                      Show all help options
  --help-gtk                      Show GTK+ Options
  --help-terminal                 Show terminal options
  --help-window-options           Show per-window options
  --help-terminal-options         Show per-terminal options

GTK+ Options
  --class=CLASS                   Program class as used by the window manager
  --name=NAME                     Program name as used by the window manager
  --gdk-debug=FLAGS               GDK debugging flags to set
  --gdk-no-debug=FLAGS            GDK debugging flags to unset
  --gtk-module=MODULES            Load additional GTK+ modules
  --g-fatal-warnings              Make all warnings fatal
  --gtk-debug=FLAGS               GTK+ debugging flags to set
  --gtk-no-debug=FLAGS            GTK+ debugging flags to unset

Options to open new windows or terminal tabs; more than one of these may be specified:
  --window                        Open a new window containing a tab with the default profile
  --tab                           Open a new tab in the last-opened window with the default profile

Window options; if used before the first --window or --tab argument, sets the default for all windows:
  --show-menubar                  Turn on the menubar
  --hide-menubar                  Turn off the menubar
  --maximize                      Maximize the window
  --full-screen                   Full-screen the window
  --geometry=GEOMETRY             Set the window size; for example: 80x24, or 80x24+200+200 (COLSxROWS+X+Y)
  --role=ROLE                     Set the window role
  --active                        Set the last specified tab as the active one in its window

Terminal options; if used before the first --window or --tab argument, sets the default for all terminals:
  -e, --command                   Execute the argument to this option inside the terminal
  --profile=PROFILE-NAME          Use the given profile instead of the default profile
  -t, --title=TITLE               Set the initial terminal title
  --working-directory=DIRNAME     Set the working directory
  --wait                          Wait until the child exits
  --fd=FD                         Forward file descriptor
  --zoom=ZOOM                     Set the terminal?s zoom factor (1.0 = normal size)

Application Options:
  --load-config=FILE              Load a terminal configuration file
  --no-environment                Do not pass the environment
  --preferences                   Show preferences window
  -p, --print-environment         Print environment variables to interact with the terminal
  -v, --verbose                   Increase diagnostic verbosity
  -q, --quiet                     Suppress output
  --display=DISPLAY               X display to use

Define the title for new terminal window.

$ gnome-terminal --title "GNOME terminal"

Simple as that!