Where does the word diaspora come from?

di·as·po·ra  
/dīˈaspərə/
Noun
  1. Jews living outside Israel.
  2. The dispersion of the Jews beyond Israel. The main diaspora began in the 8th–6th centuries bc, and even before the sack of Jerusalem...

Though living in different countries across the world the diaspora expressed a shared culture and a belief that one day all Jews would be reunited (in the Biblical Promised Land).

In modern times the term is sometimes used more generically to describe all communities of immigrants  with a shared sense of 'home'.  A recent article in The Economist, The Magic of Diasporas, suggests that these diaspora are playing an increasingly important role in the world economy
There are now 215m first-generation migrants around the world: that’s 3% of the world’s population. If they were a nation, it would be a little larger than Brazil. There are more Chinese people living outside China than there are French people in France. Some 22m Indians are scattered all over the globe.  
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