Simon Armitage provides a wonderfully funny definition of "household names" in his article on war poetry in the Times:

"Wilfred Owen and Siegfried Sassoon are still household names (that is, the answers to questions in the earlier rounds of Who Wants to Be a Millionaire?) ..."

Try watching "Who Wants to Be a Millionaire?" in a country that you did not grow up in. For you, the hardest questions will be the early ones about idioms and common cultural references in that country. Even if you speak the language very well, you'll still regularly struggle with an idiom or two! A "household name" in one country is completely obscure in another. (Try talking about baseball players with the Swiss!)