WALL (O. Eng. weal, weall, Mid. Eng. wal, walk, adapted from Lat. vallum, rampart; the original O. Eng. word for a wall was wag or wdh}, a solid structure of stone, brick or other material, used as a defensive, protecting, enclosing or dividing fence, or as the enclosing and supporting sides of a building, house or room. The Roman vallum was an earth rampart with stakes or palisades (vallus, stake; Gr. ^Xos, nail) and the Old English word was particularly applied to such earth walls; for the remains of the Roman walls in Britain see BRITAIN. The word, however, was also applied to stone defensive walls, for which the Latin word was murus. The history of the wall as a means of defence will be found in the article FORTIFICATION AND SIEGECRAFT, the architectural and constructional side under the headings ARCHITECTURE, MASONRY and BRICKWORK. In anatomy and zoology the term " wall," and also the Latin term paries, is used for an investing or enclosing structure, as in " cell-walls," walls of the abdomen, etc. In the days when footpaths were narrow and ill-paved or non-existent in the streets of towns and when the gutters were often overflowing with water and filth, the side nearest to the wall of the bordering houses was safest and cleanest, and hence to walk on that side was a privilege, hence the expressions " to take " or " to give the wall." The term " wall-rib " is given in architecture to a half-rib bedded in the wall, to carry the web or shell of the vault. In Roman and in early Romanesque work the web was laid on the top of the stone courses of the wall, which had been cut to the arched form, but as this was often irregularly done, and as sometimes the courses had sunk owing to the drying of the mortar, it was found better to provide an independent rib to carry the web; half of this rib was sunk in the wall and the other half moulded like the transverse and diagonal ribs, so that if the wall sank, or 'if it had to be taken down from any cause, the vault would still retain its position.
The word " wall eye " or " wall-eyed " is applied to a condition of the eye, particularly of a horse, in which there is a large amount of white showing or there is absence of colour in the iris, or there is leucoma of the cornea. It is also applied to the white staring eyes of certain fishes. The word has no connexion with "wall " as above, but is from the Icelandic vagleygr, vagi, a beam, sty in the eye, and eygr, eyed.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)