Desire, urge; from the Spanish verb ganar, to win or gain. The term was popularized among English speakers by the LA mathematics teacher Jaime Escalante as played by Edward James Olmos in the movie Stand and Deliver.
"You're going to work harder here than you've ever worked anywhere else. And the only thing I ask from you is ganas. Desire... If you don't have the ganas, I will give it to you, because I'm an expert." (from Stand and Deliver)