When I try to plot a graph on GNU Octave, and try to use plot, it gives me the following output
set terminal aqua enhanced title \"Figure 1\" size 560 420
I've got this problem too and solved by installing an Aquaterm for mac as mentioned here.
p.s. If you get warnings like "warning: could not match any font: *-normal-normal-10" as I did, try to check your /usr/local/etc/fonts/fonts.conf