"ll" in Spanish is pronounced like a "ya" sound, as in 'tortilla,' and "j" in German, for instance (and probably other languages I am ignorant of), is pronounced like a "ya" sound, as in "ja" ... "yes"! so I think you have a point.

The original, German name of 'Vienna' is 'Wien,' (pronounced "Veen") which in French is written 'Vienne.' I have a feeling the city's name was so written by the French to help people understand how the natives pronounced it.