One of the mysteries of the English language finally explained.
Heraldry. A charge in the form of a lozenge, with a round hole in the middle through which the field appears.
Mid 17th century; earliest use found in George Havers (fl. 1665). From French † rustre, alteration of Middle French, French ruste, itself an alteration of Middle French rute from Middle Dutch rute rhombus (also in specific heraldic use; Dutch ruit), of uncertain origin, perhaps an extended use of the plant name rute, on account of the pattern formed by the tips of its petals.
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