Tenth Day of Christmas

On the tenth day of Christmas my true love gave to me... ten lords-a-leaping. 

Who were these Lords, and why were they leaping? The only Lords that spring to my mind are members of the upper house in Parliament... the Lords Temporal and Spiritual. My memory is foggy as to whether or not I have ever met one of these Lords (Peers of the Realm). I certainly have written a few letters to some of them though, in my armchair activism mode. A full list of members of the House of Lords can be found here.