“By the left, quick march”, may seem innocuous enough, but to the ancients it sent a clear message to the enemy, no quarter would be given. Throughout recorded history the left side was associated with ill-fortune.
In Hebrew, Samael, was the Prince of Demons and 'se'mol' means left side. The word Satan (Hebrew for adversary) has no connection with the left but by the Middle Ages, Christians merged Satan and Samael and the left side took on a darker meaning. Sinister originally referred to a pocket in a toga which was on the left hand side but from this time onwards sinister and the dark side became synonymous in common terminology. Sorcery rituals used the left hand for evil and the right for good and during the infamous witch trials the mark of the devil was considered to be found on the left eyelid, shoulder or inner thigh. A common belief was witches caused injury by the touch of the left hand.
In Ancient Egypt it was the custom to enter a haunted house with the left foot first. Augustus Caesar, (63 B.C. - 14 C.E.) took care to ensure the right foot only crossed the threshold first when people entered his presence.
The custom prevailed through the reign of Emperor Nero (54-68 A.D.) when Gaius Petronius (27-66 A.D.), the judge of elegance (arbiter elegantiae) had servants trained to ensure only the right foot crossed the threshold when entering and leaving the Royal presence. Today whilst the origins may well be lost the footman forms part of the official Royal household.