Avis Cross
Avis is from the old French girl's name Avice, associated with a Latin word Aviz meaning 'bird' and hence the English word 'avian', 'aviation", etc. The Avis Cross is a cross adorned with lily petals at the arm-ends and similar to the Calatrava Cross. Not only do the arm-ends represent flowers, but they also have the appearance of a barbed fighting spear. Therefore these crosses are used mainly in heraldry, especially in southern Portugal.
The Military Order of Aviz is a Portuguese Order of Chivalry, which traces its history back to the Knights Templar who fought the Moors. They were called the 'Knights of St. Benedict of Aviz' founded in 1162, or 'Friars of Santa Maria of Évora'. They received assistance from the neighbouring Cistercian Calatravans and adopted a similar white habit emblazoned with a vert Fleur de Lis Cross.
João I, Fundador da Dinastía de Avis
The Avis Cross represents the Portuguese independence from the Castile Kingdom, following the Battle of Aljubarrota in 1385. It was used in the coat of arms of the Aviz (Joannine) Dynasty, which ruled Portugal from 1385 to 1580, after John, Master of the military Order of Aviz, became John I of Portugal.
Portugal became a republic after the revolution of 1910 and many such orders of chivalry were abolished. After the First World War, however, some orders were revived (in little more than name only) to give orders of merit to those giving outstanding service to the state.
The Military Order of Aviz, the Military Order of Christ and the Military Order of St. James of the Sword are collectively known as Ancient Military Orders. Any one of these may be awarded to deserving Portuguese or foreign civilians and military.
Trivia
The Avis Cross is part of the logo for Lusa, the 'Associação Portuguesa de Desportos' football club of São Paulo.
The AVIS car rental company has no particular connection with Portugal's history; the company was simply named after its founder, Warren Avis.
In the Harry Potter book, Avis is a magical charm where a flock of attacking birds emerge from the magician's wand.