Anisha Gupta, returning clothes to a Hugo Boss store on Rodeo Drive in Beverly Hills, shrugged when asked about Libor. She had heard the term. She wasn't sure she could define it.

"I thought it was a pill," said Gupta, an unemployed 27-year-old who lives in Los Angeles.

Americans are getting a crash course as a once obscure acronym weighs on the economy. In interviews across the country, oil workers, ministers, bank managers and politicians said they were baffled by the London interbank offered rate or fearful of its surge this week. They agreed Libor was important, even if they couldn't put their finger on why.

"Without getting real specific, I think I'm probably not competent to be talking about what is happening overseas," said Sen. Jon Kyl, an Arizona Republican who helped shepherd passage of a $700 billion bank bailout as his party's No. 2 official. "It's all happening very rapidly."

Libor, set every morning in London, is what banks pay to borrow money from each other. That in turn determines prices for financial contracts valued at $393 trillion as of Dec. 31, 2007, or $60,000 for every person in the world, and helps set consumer interest rates on everything from home loans to credit cards.

In recent weeks, as governments in Europe rescued five banks and the U.S. debated a bailout, the cost of one-month bank loans in euros and overnight dollar loans soared to records. In practice, that means banks are hoarding cash, raising borrowing costs and slowing economies worldwide.

Still, explaining Libor can be a challenge.

"What you have been seeing in the destruction of Libor in the last months, I cannot really point to that point and say this has impact on car sales," Fritz Henderson, the chief operating officer of General Motors Corp., said in a TV interview. "But certainly it is very destructive."

The complexities showed during the bailout debate in Congress.

"Very few Americans have ever heard of something called the Libor," said Senate Banking Committee Chairman Christopher Dodd, a Connecticut Democrat. He defined the term, then said, "Libor jumped over 400 percent in just one day."

Actually, overnight dollar loans rose 168 percent on Sept. 30, to a record 6.8 percent from 2.6 percent. Dodd was probably referring to the increase in basis points, or hundredths of a percent, which was 431. A spokesman at Dodd's office in Washington who didn't identify himself said when asked about that: "I'm sorry. Libor?"

Hits on Internet search engine Google show interest is increasing. In 2007, the U.S. wasn't in the top 10 countries where people searched for the term. Over the past 7 days, the U.S. has surged to No. 2, behind the Czech Republic, where Libor is a common first name. Worldwide, the number of hits rose tenfold from Sept. 7 to Sept. 30. White House spokesman Tony Fratto said at a press briefing last week that officials closely watch Libor, then paused.

"Raise your hand if you're familiar with the Libor rate," he said to two dozen reporters. Only one did, drawing nervous chuckles.

Libor is actually a set of rates, calculated for several currencies on periods ranging from overnight to 12 months. The British Bankers' Association compiles the dollar rate every day from data submitted by 16 banks, including Deutsche Bank AG and Royal Bank of Scotland Group Plc. There are also rates for the euro, Japanese yen, British pound, Swiss franc, and Australian and Canadian dollars.