Katie Couric's Notebook: Lame Duck

Members of the 111th Congress .. many of whom were not re-elected two weeks ago .. have returned to work.

It's called a lame duck session.

But, with apologies to the Marx Brothers, why a duck?

The term was first used in 18th century London to describe a stock broker who could not pay his debts .. and was thus as powerless as a lame duck.

It was first applied to American politicians in the mid 19th-century - and now commonly refers to those who've lost re-election or are not running again but are still in office - their power greatly reduced.

Originally, the Constitution required Congress to meet once a year, in December.

With elections held in November, but the new Congress not sworn-in until March, that meant a mandatory lame duck session.

That changed in 1933, when the 20th Amendment said Congress must meet -- and the new members take office -- on the same day .. January Third .. making it all just .. ducky.

That's a page from my notebook.

I'm Katie Couric, CBS News.