When we first moved here, I assumed that people with the last name Bosch had some German ancestor. The more people I met, the more unlikely this theory became.
The oldest reference I found was a 1510 census of Valencia, which showed that Bosch was already a relatively popular surname. A random fact that struck me was that out of 4850 people recorded, 4602 only had a single surname. This was about 270 years after Valencia was re-conquered from the Moors.
It was also interesting to read about the Morisco Expulsion, where around 1600, about 300,000 people suspected of being of Moorish descent were deported from the kingdom of Aragon.
Many of them were sent to Marseille, which perhaps explains why people in the ex-kingdom of Aragon are somewhat lighter-skinned than people from other parts of Spain and why people from the south of France are darker-skinned.