The Australian Museum has the origin of this cockroach as Africa, although other sources give Northern Africa as the source of the American cockroach, arriving at the time of the slave trade.
It seems to be generally thought the German cockroach came to Europe from south-east Asia along 17th century trade routes at about the time of Marco Polo. These cockroaches are associated with human activities and habitation and where conditions are moist and humid. It is also called the Asian or Chinese cockroach or the Russian roach by the Germans, Polish roach by the Russians, French cockroach by Portuguese depending prejudices. Another example of this is our European wasps, which are called Asian wasps in France and Europe. We could hypothesise that this species kept its name in Australia as a result of the 2 world wars.
The German Cockroach was certainly common in Germany in the past, and can still be found there today.
Blatella germanica was named by Carl Linnaeus, the Swedish "father of Taxonomy", in 1767 probably because they were common when he travelled in Germany in the 18th century.
There are a number of fun reasons why people believe they are not found in Germany:
- The German people are so neat, clean and tidy
- There are several regulations mandating clean workplace conditions
- The Germans clean up dog faeces
- Cold winter conditions do not suit the species.
There are a number of theories as to why he chose the name German cockroach:
- He had seen them when travelling in Germany (Sweden was too cold for the species
- He encountered them in goods sent from Germany and his common name became the Latin or scientific name.
- As an insult to the Germans or Germany as for some reason he may not have liked the country or culture
- Apparently Linnaeus liked naming pest or ugly species after people or countries he was not fond of.
The University of Massachusetts has a question and answer on this subject whihc may also be of interest.