I didn't know there was a 12th century accordion, unless its something else called an accordion, but I don't think the word accordion even existed in those days - too complicated a word for people of the 12th century.
I`m not 100% sure if this is correct Chronologically but apparently the designer of that first squeezebox travelled all over Europe with it and at one point was in Italy , stayed at a farm owned by the Soprani Family for a night and one of the sons of the farmer, Paolo, copied the design drawings ---- the rest is History .
I believe the origins of the European accordion was the Sheng - a reed instrument brought back from China by a Jesuit priest.
In England Wheatstone - later a famous physicist - invented the Symphonium (1829) - essentially a sheng with metal reeds and buttons to unstop them.
He would have been really fed up had he known about the twelfth century bellows as it took him a while to transform the Symphonium into the English concertina.
Amazing , I thought a Symphonium was a type of music box with interchangeable "records" ..... The Sheng sounds interesting ..... I`d like a Martin Horn (a really bizarre Free reeder like a cross between a trumpet and a bicycle horn)