Diaspora, as originally coined, referred to the dispersion of the Jews.

Yes, but it's a short hop, skip, and a jump from the original Jewish Diaspora to A-H's "dispersion of an originally homogeneous entity, such as a language or culture".

http://www.bartleby.com/61/1/D0200100.html

The word, diaspora after all conceivably existed in Greek before the Jews were dispersed outside of Israel in the sixth century BCE.

Vulgate: et dispergam eos ventilabro in portis terrae

LXX: kai diaspero autous en diaspora en pulais laou mou eteknothesan.

KJ: And I will fan them with a fan in the gates of the land.

Jer. xv:7.