Stands for: Northern rim countries -- Canada, Russia, Scandinavia, and the northern United States
Created by: University of California/Los Angeles geographer Laurence C. Smith
Why: Smith believes access to shipping lanes opened up by the melting of Arctic ice, combined with abundant oil and natural gas resources, will make the Arctic countries the pivotal powers of the late 21st century.
Stands for: Portugal, Italy, Greece, Spain
Why: It's not clear who coined the unflattering nickname, which groups the worst-performing European economies, but it's become widespread during the euro crisis and is sometimes spelled "PIIGS" to include Ireland.
Stands for: Turkey, India, Mexico, Brazil, Indonesia
Created by: George Mason University professor Jack Goldstone
Why: Goldstone argued in a 2011 ForeignPolicy.com article that economic growth in Russia and China would be hampered by shrinking working-aged populations, so India and Brazil should more accurately be placed with countries that boast growing economies and populations.