The word “Aspirin” was once the exclusive Bayer trademark for acetylsalicylic acid (ASA). The first use of what became known as aspirin was by the Greek physician Hippocrates, who used powder extracted from the bark of a willow tree to treat pain and reduce fever. The bark contained salicin, a component of acetylsalicylic acid. Salicin was successfully isolated from willow bark in 1829 but it often irritated the stomach. Two years after a young Bayer researcher, Felix Hoffman, synthesized acetylsalicylic acid, Bayer registered the trademark “aspirin” on March 6, 1899.