From ancient Greek χοάνη "funnels, funnel-shaped openings".
Choana - internal nostrils, by which the posterior nostrils of bivalve fishes open into the oral cavity. Among fishes they are peculiar only to bipedal fishes.
The choana first appeared in brush-feeding and double-breathing fishes. In the embryos of bipedal fish, the grooves in the olfactory fossa turn into channels whose inner openings, called primary choanae, open into the oral cavity. When bipedal fish breathe air, the airflow passes through these channels to the lungs.