Hyakudo or o-hyakudo means 'a hundred times' and can refer either to a hundred visits (i.e. many visits) to a shrine or to the practice, found in some shrines, of circumambulating or walking backwards and forwards between two stone markers set in the grounds. This is done either a hundred times, or alternatively a number of times derived from the number of years of one's age, e.g. eleven times (six times plus five) for a sixty-five year old. It may be performed for a variety of reasons; as penance, to heal an ailment, to demonstrate sincerity when seeking help from the kami or as mild asceticism.
A Popular Dictionary of Shinto. Brian Bocking.