The leafy ornament used in the capitals of Corinthian and
composite columns. It is said that Callimachos lost his daughter, and
set a basket of flowers on her grave, with a tile to keep the wind from
blowing it away. The next time he went to visit the grave an acanthus
had sprung up around the basket, which so struck the fancy of the
architect that he introduced the design in his buildings.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894