Not unusual, but to me interesting:

Diaper:
1) Surface ornament of repeated straight-sided geometrical shapes, lozenge, triangle, etc.
(Martindale, Andrew. Gothic Art, 268)

2) All-over decoration of surfaces with small pattern such as flowers in squares, lozenges, etc. Carved
examples characteristic of the 13th and 14th centuries; in the 15th century used for painted ornament.
Perhpas derived from patterned cloth from Ypres in Belgium (Dyaper, i.e. D'Ypres).
(Wood, Margaret. The English Medieval House, 411)