The Probert Encyclopaedia of Architecture

ORIEL

In architecture, an oriel or orioke is a porch or balcony at the head of an outdoor staircase.

The derivation of this term is unknown, and its original meaning involved in obscurity. It was formerly used in various senses, and in order to suit all the objects to which it is applied it must be described as a projection from a building, such as a penthouse or porch, to give shelter; a recess within a building, such as a closet, bower, or private chamber; an upper story, or a gallery; in the present day the name is only used in reference to a projecting window, which is frequently called an oriel or oriel window, but it does not appear ever to have been used anciently in this sense;
the old term for these windows is bay-window.
Research Oriel