The name giver:
Monet painted the famous Impression, Sunrise (Impression, soleil levant) in 1872. It depicted a Le Havre port landscape. In 1874 it hung in the first Impressionist exhibition. Thanks to this painting the whole movement is now called “Impressionism” – The art critic who came up with this adjective meant his assessment to be negative, but the Impressionists at the time approved of description and it stuck.