Though the term "ethnobotany" was not coined until 1895 by the US botanist John William Harshberger, the history of the field begins long before that.
In Pythagoreanism which originated in 500 BC refused to eat beans because of the human relationship to it through matter. In A.D. 77, the Greek surgeon Dioscorides published "De Materia Medica", which was a catalog of about 600 plants in the Mediterranean. It also included information on how the Greeks used the plants, especially for medicinal purposes.
This illustrated herbal publication contained information on how and when each plant was gathered, whether or not it was poisonous, its actual use, and whether or not it was edible (it even provided recipes). Dioscorides stressed the economic potential of plants. For generations, scholars learned from this herbal publication, but did not actually venture into the field until after the Middle Ages due to the Inquisition. [**]
Image: Plants have been widely used by American Indian healers, such as this Ojibwa man.