Why did the chalice become a symbol of the Hussite movement?

The chalice became the defining symbol of the Hussite movement because it represented a central demand of the followers of Jan Hus: the restoration of the Eucharist to the laity "under both kinds" (sub utraque specie).1

While the Roman Catholic Church had restricted the consumption of wine during communion to the clergy, the Hussites argued that all believers should receive both the bread and the wine. This practice, which gave rise to the term Utraquist (from the Latin utraque, meaning "each of two"), became a primary point of contention and a mark of their reformist identity. To signify this commitment to the equal spiritual standing of the laity, the followers of Hus emblazoned the chalice on their banners and flags.21