1560s, "break or opening in a material object," from Latin hiatus "opening, aperture, rupture, gap," from past participle stem of hiare "to gape, stand open" (see yawn (v.)). Sense of "gap or interruption in events, etc." is first recorded 1610s.
hiatus hi·a·tus (hī-ā'təs)
n. pl. hiatus or hi·a·tus·es
An aperture or fissure in an organ or a body part.