The term "wall-eyed" originates from Old Norse vald-eygðr, meaning 'having beamy or glaring eyes'. The first element is related to Old Norse valr, referring to a beam or a staff, which influenced the Middle English understanding of 'wall' in the sense of something broad and blank. Over time in English, the 'wall' component became associated with the visible white sclera of the eye when it turns outward, resembling a pale, broad surface. Thus, the literal imagery of a 'wall-like eye' evolved to describe the specific medical condition of exotropia and, by extension, the bulging or staring eyes of certain animals.

Structure: wall + eyed - wall: From Old English weall, meaning a rampart or a structure for defense. In this compound, it functions metaphorically to suggest something broad, blank, or prominent like a wall. - eyed: From Old English ēaged, the adjectival form of ēage (eye). It functions as a suffix meaning 'having eyes of a specified kind'.