Lookups on Merriam-Webster began spiking around May 1, 2010.
Austerity figured prominently in news coverage of the economic panic and protests triggered by the debt crisis in Greece.
For example, as the New York Times reported,
"The Greek Parliament passed a package of tough austerity measures on Thursday, trying to stave off economic collapse and help prevent debt contagion from spreading." (Dan Bilefsky, May 5, 2010)
The definition for this sense of austerity says it all: "enforced or extreme economy."
The word's origins are - coincidentally - Greek; austerity comes from austēros, meaning "harsh" or "severe."