More on Knights of the Swan from Infoplease:

• Knights of the Swan - Knights of the Swan An order of the House of Cleve. Source: Dictionary of Phrase and Fable, E. ...
• Swan - Swan Fionnuala, daughter of Lir, was transformed into a swan, and condemned to wander for many ...
• Dictionary of Phrase and Fable: K - Definitions, origins, and illustrative excerpts for words, phases, and literary allusions starting with "K"