(one's) tongue hangs out
One thinks of or anticipates something with great desire and eagerness. Our tongues hung out at the thought of how much money could be made with such a scheme. He stared at the all-you-can-eat buffet with his tongue hanging out.
tongue hangs out, one's
One is eagerly anticipating something, as in Their tongues were hanging out at the thought of seeing the movie stars in person. This expression alludes to an animal's tongue hanging out of its mouth in anticipation of food. [Late 1800s]