Lords A-Leaping Number is a term used to describe the number TEN. It is derived from the traditional English Christmas carol, 'The Twelve Days of Christmas'. The song lists a series of gifts given by a suitor to his beloved on each of the twelve days leading up to Christmas. On the tenth day, the suitor gives 'TEN lords a-leaping'. This phrase has been used to refer to the number TEN in a humorous way.