How to set the title for GNOME terminal emulator

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))
        continue;
      else if (c == ';')
        break;

      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

Usage:
  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!