Well it depends on what you mean, really. The first in the Star Wars universe (BBY/ABY) or in ours (1978 AD) ?
i,being the person asking the question, mean in the star wars universe.(bby/aby)
Then the earliest one I can think of is in KotOR. I think Bastilla says it to you or something.
That is unknown. I am pretty sure someone said it before Bastilla however.