Beloved David Shepherd lifted one foot off the ground whenever the score reached 111 (or 222, 333 etc). I mean nelson is supposed to be bad omen for batsman so why He as an Umpire used to do that in a match.
This is pretty well covered by Cricinfo's obituary of Shepherd; remember that Shepherd was a competent first-class player for Gloucestershire before he was an umpire:
Why did it become associated with jumping up and down? Supposedly this started in the Gloucestershire dressing room when Shep was a player. Some believed that having no part of your body touching the floor brought better luck.
Shep says: "Whenever I was in the field as a player and the score was 111, I would do a little jump but no one really knew I was doing it except one or two friends. When I did my second Test as an umpire at Edgbaston, in 1985, someone had written in to dear old Brian Johnston and said `Watch this idiot when the score gets on 111.'