The most characteristic coin of the Christian Middle Ages in all of Europe, at least until the 13th century, was the denier, “dinero” in Spanish, a name derived from the old Roman denarius.
The first Christian issues on the peninsula—produced in the Spanish March, a buffer zone established south of the Pyrenees by the Carolingian Empire to halt the Islamic advance—, were the silver deniers of Charlemagne minted in what is now Catalonia after 785.
The rest of the fledgling Christian kingdoms would not make their own coins for another two centuries. This remarkable backwardness, in comparison to their Hispano-Islamic neighbours, was due to their different political, economic and social structure. When coins were necessary, they used the Islamic currency that was already circulating throughout the Iberian Peninsula. They finally began minting their own coins in the late 11th century, when urban life and trade flourished thanks to the economic boost of the Way of Saint James and territorial and political consolidation.
Each kingdom devised its own monetary system, with different values and types that combined likenesses of their kings, religious symbols (especially the cross), heraldic emblems and legends in Latin. However, they were all united by the billon denier: a small, modest, thin, fragile coin.