meshuggener

Merriam-Webster's Word of the Day for April 02, 2011 is:

meshuggener • \muh-SHUG-uhner\  • noun
: a foolish or crazy person

Examples:
Alex wondered what kind of meshuggener would be foolish enough to buy bonds from a known scam artist.

'Take no notice,' she said…. 'The man's a meshuggener.' -- From Howard Jacobson's 2010 novel The Finkler Question

Did you know?
From bagel and chutzpah to shtick and yenta, Yiddish has given English many a colorful term over the years. Meshuggener is another example of what happens when English interprets that rich Jewish language. Meshuggener comes from the Yiddish meshugener, which in turn derives from meshuge, an adjective that is synonymous with crazy or foolish. English speakers have used the adjective form, meshuga or meshugge, to mean foolish since the late 1800s; we've dubbed foolish folk meshuggeners since at least 1900.