Gnuplot can read column names from the first line, but you can still specify the column names normally as well. Therefore, this effectively skips the first line.
Issue the command
set key autotitle columnhead
This tells gnuplot that the first line is not data, but is the column names to be used for the key. You can still unset key or plot datafile title sometitle the same as you could before, and gnuplot will just not use that data.
Suppose that my file looks like
1 2
4 5
7 8
I can just issue set key autotitle columnhead follwed by unset key (if I don’t really want a key), and it will skip the first line.
Alternatively, I can pipe my data through an external program. For example, using awk (which is available for most OS’s including Windows), I can do
plot "< awk '(NR>2){print;}' datafile"
to skip the first 2 lines (using Windows, I must do '< awk "(NR>2){print;}" datafile'). If I don’t want to keep typing this, I can store this in a string
skipfile = "\"< awk '(NR>2){print;}' datafile\""
and use it as a macro (for Windows, use skipfile=""< awk \"(NR>2){print;}\" datafile""). For instance, to plot the datafile using lines, I might do
plot @skipfile with lines
The @skipfile just tells gnuplot to treat the command like I had just typed the contents of skipfile right there.