1An item of cloth, paper, etc., fixed on the surface of something, especially for decorative effect; a thin piece of leather, etc., mounted on the cover of a book for ornamentation.
An occlusal rest extended so as to cover the whole occlusal surface of a tooth.
Late 19th century; earliest use found in The Century Dictionary. From onlay.
To lay on (literal and figurative): see to lay on.
Old English; earliest use found in Old English Martyrology. From on- + lay.