The prefix "giga" means a billion; in computer science sometimes it means 1024 cubed, which is about 7% more than a billion.

Some people believe that the prefix originated in a humoristic poem by the German poet Christian Morgenstern. The poem is called "Anto-logie" (Ant-ology). German-speaking readers will easily find it on the Internet; the relevant parts are at the beginning:

Im Anfang lebte, wie bekannt,
als größter Säuger der Gig-ant.

Wobei gig eine Zahl ist, die
es nicht mehr gibt, - so groß war sie!

Doch jene Größe schwand wie Rauch.
Zeit gab's genug - und Zahlen auch.
...

Translation:

In the beginning, as is well known,
the largest mammal in existence was the gig-ant.

Where "gig" is a number that
no longer exists - since it was so large!

This size, however, dissipated like smoke.
There was enough time - and enough numbers.


(Note that faithfully translating an entire poem by Morgenstern - even without the verses - is very tricky, since they usually use a lot of plays on words. I would certainly not do it, though I did see great translations of some of his poems.)