Follow the Money Mist
According to a long historic story... The use of thieves oil dates back to the 1400's. The time of the infamous Bubonic Plague(aka The Black Death) that devastated a large portion of France. The Black Death spread like a wild-fire amongst the citizens. It seemed impossible to be in the vicinity without contracting it, and in those times, the sickness really meant death.
At the time, however, four thieves were captured and charged for stealing from the dead. The thieves never contracted the plague, despite the close contact with the Black Death victims. The judge was so intrigued by how these men stayed immune to this terrible disease, that he told them if they shared their secret he would spare them of burning them alive.
The thieves told the judge their secret: They were perfume & spice merchants who were unemployed due to the closure of the sea ports and the devastation of the plague. They had prepared and essential oil recipe that when applied to their hands,ears,temples,feet & mask over their mouths, kept them safe from infection. The men were not burned alive, instead they were hanged for their crimes.
From then on, the doctors who treated the Black Plague victims put the herbal infusion on their hands,ears,temples and feet, and wore beak like masks stuffed with cloths containing this special blend of essential oils for protection.