I’ve assumed that flamenco has always been a Spanish word for a dance, but Michael Quinion in his excellent newsletter (recommended reading) says:
A direct Flemish connection is actually more plausible. From 1579 to 1700 Flanders was part of the Spanish Netherlands and Spanish fighting men were based there. This is why one sense of “flamenco” in Spanish is of a soldier. It has been suggested that some of them were Roma and that on their return to Spain they were given special dispensation to live where they wanted and take any occupation they liked, unlike other Roma, who continued to suffer severe legal restrictions. In consequence, some Roma families of Andalusia were given the title of “los flamencos”, the Flemish ones (George Borrow mentions this in Zincali) and the art form was taken from this.
Any further suggestions?