The akker is not a unit of measurement anymore in mainland Europe, it is any
field used for growing crops. A large farmer may possess 120 ha of
'akkerland'.
Its former use of a unit of measurement can be traced back in names of
villages and townlands, like Tienakker or Vieracker.
Before metrication it was used alongside the morgen and many other agrarian
units. It was roughly 0.5 ha. An akker can have any area now.
It is possible that the British acre has been used in Italy in the past,
that unit was called acro. I wonder how it could migrate that far.
The origin of the acre goes back to ancient Greek and Latin. It can be found in several modern European languages, although with shifting meanings.
Han added:
The unit of 500 g, called pond, Pfund livre etc. on the other hand is used
very much while shopping.
Before the Revolution the French "livre" varied from 380 to 550 grams. It is now recognized as 500 g. I suspect that the German Pfund and the Dutch pond underwent a similar transformation.
