People in the United States celebrate Lame Duck Day every year on February 6. The word ‘Lame Duck’ has nothing to do with this day. The 20th amendment to the US Constitution addressed Presidential succession. That year on February 6 people observed first Lame Duck Day.
Lame Ducks are those who fail to hold a position in an election. So now he becomes toothless or totally ineffective. Lame Duck is mainly the person who was the U.S. President in the previous term but now he is not.
When immediate President again participates in the next election and if he fails to bag the maximum vote, he will be no more a President. He has nothing to do without stepping down from the position.
That is why people celebrate this day to recognize the lame ducks and show respect for them.