Back to original question - why does my prompt change to "arg: 3" when I hit Alt+3?

[Chris G]

OK, so Alt+character doesn't work as I expect in xfce4-terminal.  :-)

Can anyone explain why it does what it does?  When I hit Alt+<digit>
my bash prompt changes to "(arg: <digit>)", hitting further Alt+<digit>
keys adds digits to the prompt so that hitting, for example, Alt+5,
Alt+4, Alt+3, Alt+2 gives me a prompt (arg: 5432).

Ah, what it does is to repeat the next character entered arg times, what
an extremely un-useful facility, does anyone have any idea where it
comes from?  It's not from bash because the same thing happens within my
editor. 

-- 
Chris Green