The name knapweed is from the German word knobbe, which means a bump or button. Other common names are hardhead and blue bottle. It was also known as bachelor's button, since the bud resembled a kind of button.
At one time English girls wore these bachelor button flowers as a sign that they were eligible to marry. It was also thought that if the girl hid this flower under her apron she could have the bachelor of her choice.
The name corn flower was given to this plant because it was often found grown in farm fields.