Penury means extreme poverty to the point of homelessness and begging in the streets. Economic downturns, job loss, shopping sprees, and weekends at the high rollers' table in Vegas can lead to penury.
Penury comes from the Latin word penuria, which, though it sounds like something contagious, actually means scarcity. It's not a word that turns up often in casual conversation or even on nightly newscasts. You're more apt to spot it in a college textbook or maybe an editorial in The New York Times.