Yoke! that's it.
Thanks for putting me out of my misery HB
Origin of the Yoke, arrows and Gordian knot.
Emblems of the Catholic Monarchs on the facade of the Church of Santiago (Losar de la Vera, Cáceres), c. 1500.
In Spanish heraldic tradition, the yoke, set of arrows and the Gordian Knot, were elements which were joined with the leaves and the pomegranate and the motto Tanto monta, monta tanto (Equal opposites in balance), the personal motto and prenuptial agreement of the Catholic Monarchs Isabella I of Castile and Ferdinand II of Aragon, as embodied in the song of Pedro Marcuello. This motto was used upon the weapons of both Monarchs from 1475. They made an agreement, now called Concordia de Segovia and the coat of arms is a graphic representation of this pact which united the two most important Monarchs on the peninsula. It is the oldest known image of the escutcheon.
The bundle of arrows may have its origins in the Roman fasces, a bundle of rods and an axe with the blade projecting, that were carried before the magistrates to show their power. The arrows pointed downward to show they were ready for use in executing criminals or for warfare. With the marriage of Ferdinand and Isabella, the bundle of arrows meant the union of Castile and Aragon to create Spain. The yoke was Isabel's and the arrows Ferdinand's. The F was the first letter of Fernando's name, and the Y the first letter of Isabella's. The Gordian knot, cut, united the two. The number of arrows varied, but always pointed downwards. Over time, the badge of the Catholic Monarchs spread to other heraldic compositions, and was adopted in some of its variants as the emblems of not only towns and cities such Ronda, Marbella and Málaga, but also Puerto Rico and the Netherlands.