also eye-hole, 1630s, "cavity or socket containing the orbit of the eye," from eye (n.) + hole (n.). By 1856 as "hole or opening, as in a mask or in a curtain or door, through which one may look, a peep hole."  

"small hole," late 14c., oilet, from Old French oeillet, diminutive of oeil "eye," from Latin oculus "an eye" (from PIE root *okw- "to see"). Spelling later modified by influence of eye (n.).

"sense of sight, capacity for seeing," c. 1200, from eye (n.) + sight (n.).