Dall

[…] for such machine-made slate "dalls," or tiles, as perhaps we might call them, would soon be valued by the architect and builder for the roofs of many other classes of buildings as well as ecclesiastical ones.

[…] tiling. Thus arose those admirable roofs known in France as "en dallage," of which one most instructive example to both engineer and architect may be seen in those of the clerestory roofs of Nôtre Dame at Paris. The "dalls" being hand wrought[…]